This jQuery plugin makes simple client-side form validation easy.


File structure

form-validation/
┣ js/
┃ ┗ main.js
┣ plugins/
┃ ┗ jquery.validate.js
┗ index.php

index.php

<!DOCTYPE html>
<html lang="en">
    <head>
        <meta charset="utf-8">
        <title>Client-side Form Validation Using jQuery Plugin</title> 
        <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/css/bootstrap.min.css">
        <style>
            .container{
                margin: 10px auto;
                width: 80%;
            }

            #signupForm label.error {
                margin-left: 10px;
                width: auto;
                display: inline;
                color: red;
            }
            #newsletter_topics label.error {
                display: none;
                margin-left: 103px;
                color: red;
            }
        </style>
    </head>
    <body>
        <div class="container">
            <div class="row">
                <div class="col">
                    <h1>Client-side Form Validation Using jQuery Plugin</h1>
                    <form class="cmxform" id="signupForm" method="post" action="">

                        <p>
                            <label for="firstname">Firstname</label><br>
                            <input id="firstname" name="firstname" type="text" class="form-control">
                        </p>
                        <p>
                            <label for="lastname">Lastname</label><br>
                            <input id="lastname" name="lastname" type="text" class="form-control">
                        </p>
                        <p>
                            <label for="username">Username</label><br>
                            <input id="username" name="username" type="text" class="form-control">
                        </p>
                        <p>
                            <label for="password">Password</label><br>
                            <input id="password" name="password" type="password" class="form-control">
                        </p>
                        <p>
                            <label for="confirm_password">Confirm password</label><br>
                            <input id="confirm_password" name="confirm_password" type="password" class="form-control">
                        </p>
                        <p>
                            <label for="email">Email</label><br>
                            <input id="email" name="email" type="email" class="form-control">
                        </p>
                        <p>
                            <label for="agree">Please agree to our policy</label><br>
                            <input type="checkbox" class="checkbox" id="agree" name="agree">
                        </p>
                        <p>
                            <label for="newsletter">I'd like to receive the newsletter</label><br>
                            <input type="checkbox" class="checkbox" id="newsletter" name="newsletter">
                        </p>


                        <label for="topic_marketflash">
                            <input type="checkbox" id="topic_marketflash" value="marketflash" name="topic">Marketflash
                        </label>
                        <label for="topic_fuzz">
                            <input type="checkbox" id="topic_fuzz" value="fuzz" name="topic">Latest fuzz
                        </label>
                        <label for="topic_digester">
                            <input type="checkbox" id="topic_digester" value="digester" name="topic">
                            Mailing list digester
                        </label><br>

                        <label for="topic" class="error">
                            Please select at least two topics you'd like to receive
                        </label><br>
                        <p>
                            <input class="submit" type="submit" value="Submit">
                        </p>
                    </form>
                </div>
            </div>
        </div>
        <script src="https://code.jquery.com/jquery-2.2.4.min.js"></script>
        <script src="plugins/jquery.validate.js"></script>
        <script src="js/main.js"></script>
    </body>
</html>

jquery.validate.js

/*!
 * jQuery Validation Plugin v1.19.2
 *
 * https://jqueryvalidation.org/
 *
 * Copyright (c) 2020 Jörn Zaefferer
 * Released under the MIT license
 */
(function(factory) {
    if (typeof define === "function" && define.amd) {
        define(["jquery"], factory);
    } else if (typeof module === "object" && module.exports) {
        module.exports = factory(require("jquery"));
    } else {
        factory(jQuery);
    }
}(function($) {

    $.extend($.fn, {
        // https://jqueryvalidation.org/validate/
        validate: function(options) {

            // If nothing is selected, return nothing; can't chain anyway
            if (!this.length) {
                if (options && options.debug && window.console) {
                    console.warn("Nothing selected, can't validate, returning nothing.");
                }
                return;
            }

            // Check if a validator for this form was already created
            var validator = $.data(this[ 0 ], "validator");
            if (validator) {
                return validator;
            }

            // Add novalidate tag if HTML5.
            this.attr("novalidate", "novalidate");

            validator = new $.validator(options, this[ 0 ]);
            $.data(this[ 0 ], "validator", validator);

            if (validator.settings.onsubmit) {

                this.on("click.validate", ":submit", function(event) {

                    // Track the used submit button to properly handle scripted
                    // submits later.
                    validator.submitButton = event.currentTarget;

                    // Allow suppressing validation by adding a cancel class to the submit button
                    if ($(this).hasClass("cancel")) {
                        validator.cancelSubmit = true;
                    }

                    // Allow suppressing validation by adding the html5 formnovalidate attribute to the submit button
                    if ($(this).attr("formnovalidate") !== undefined) {
                        validator.cancelSubmit = true;
                    }
                });

                // Validate the form on submit
                this.on("submit.validate", function(event) {
                    if (validator.settings.debug) {

                        // Prevent form submit to be able to see console output
                        event.preventDefault();
                    }

                    function handle() {
                        var hidden, result;

                        // Insert a hidden input as a replacement for the missing submit button
                        // The hidden input is inserted in two cases:
                        //   - A user defined a `submitHandler`
                        //   - There was a pending request due to `remote` method and `stopRequest()`
                        //     was called to submit the form in case it's valid
                        if (validator.submitButton && (validator.settings.submitHandler || validator.formSubmitted)) {
                            hidden = $("<input type='hidden'/>")
                                    .attr("name", validator.submitButton.name)
                                    .val($(validator.submitButton).val())
                                    .appendTo(validator.currentForm);
                        }

                        if (validator.settings.submitHandler && !validator.settings.debug) {
                            result = validator.settings.submitHandler.call(validator, validator.currentForm, event);
                            if (hidden) {

                                // And clean up afterwards; thanks to no-block-scope, hidden can be referenced
                                hidden.remove();
                            }
                            if (result !== undefined) {
                                return result;
                            }
                            return false;
                        }
                        return true;
                    }

                    // Prevent submit for invalid forms or custom submit handlers
                    if (validator.cancelSubmit) {
                        validator.cancelSubmit = false;
                        return handle();
                    }
                    if (validator.form()) {
                        if (validator.pendingRequest) {
                            validator.formSubmitted = true;
                            return false;
                        }
                        return handle();
                    } else {
                        validator.focusInvalid();
                        return false;
                    }
                });
            }

            return validator;
        },
        // https://jqueryvalidation.org/valid/
        valid: function() {
            var valid, validator, errorList;

            if ($(this[ 0 ]).is("form")) {
                valid = this.validate().form();
            } else {
                errorList = [];
                valid = true;
                validator = $(this[ 0 ].form).validate();
                this.each(function() {
                    valid = validator.element(this) && valid;
                    if (!valid) {
                        errorList = errorList.concat(validator.errorList);
                    }
                });
                validator.errorList = errorList;
            }
            return valid;
        },
        // https://jqueryvalidation.org/rules/
        rules: function(command, argument) {
            var element = this[ 0 ],
                    isContentEditable = typeof this.attr("contenteditable") !== "undefined" && this.attr("contenteditable") !== "false",
                    settings, staticRules, existingRules, data, param, filtered;

            // If nothing is selected, return empty object; can't chain anyway
            if (element == null) {
                return;
            }

            if (!element.form && isContentEditable) {
                element.form = this.closest("form")[ 0 ];
                element.name = this.attr("name");
            }

            if (element.form == null) {
                return;
            }

            if (command) {
                settings = $.data(element.form, "validator").settings;
                staticRules = settings.rules;
                existingRules = $.validator.staticRules(element);
                switch (command) {
                    case "add":
                        $.extend(existingRules, $.validator.normalizeRule(argument));

                        // Remove messages from rules, but allow them to be set separately
                        delete existingRules.messages;
                        staticRules[ element.name ] = existingRules;
                        if (argument.messages) {
                            settings.messages[ element.name ] = $.extend(settings.messages[ element.name ], argument.messages);
                        }
                        break;
                    case "remove":
                        if (!argument) {
                            delete staticRules[ element.name ];
                            return existingRules;
                        }
                        filtered = {};
                        $.each(argument.split(/\s/), function(index, method) {
                            filtered[ method ] = existingRules[ method ];
                            delete existingRules[ method ];
                        });
                        return filtered;
                }
            }

            data = $.validator.normalizeRules(
                    $.extend(
                            {},
                            $.validator.classRules(element),
                            $.validator.attributeRules(element),
                            $.validator.dataRules(element),
                            $.validator.staticRules(element)
                            ), element);

            // Make sure required is at front
            if (data.required) {
                param = data.required;
                delete data.required;
                data = $.extend({required: param}, data);
            }

            // Make sure remote is at back
            if (data.remote) {
                param = data.remote;
                delete data.remote;
                data = $.extend(data, {remote: param});
            }

            return data;
        }
    });

// JQuery trim is deprecated, provide a trim method based on String.prototype.trim
    var trim = function(str) {

        // https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/trim#Polyfill
        return str.replace(/^[\s\uFEFF\xA0]+|[\s\uFEFF\xA0]+$/g, "");
    };

// Custom selectors
    $.extend($.expr.pseudos || $.expr[ ":" ], {		// '|| $.expr[ ":" ]' here enables backwards compatibility to jQuery 1.7. Can be removed when dropping jQ 1.7.x support

        // https://jqueryvalidation.org/blank-selector/
        blank: function(a) {
            return !trim("" + $(a).val());
        },
        // https://jqueryvalidation.org/filled-selector/
        filled: function(a) {
            var val = $(a).val();
            return val !== null && !!trim("" + val);
        },
        // https://jqueryvalidation.org/unchecked-selector/
        unchecked: function(a) {
            return !$(a).prop("checked");
        }
    });

// Constructor for validator
    $.validator = function(options, form) {
        this.settings = $.extend(true, {}, $.validator.defaults, options);
        this.currentForm = form;
        this.init();
    };

// https://jqueryvalidation.org/jQuery.validator.format/
    $.validator.format = function(source, params) {
        if (arguments.length === 1) {
            return function() {
                var args = $.makeArray(arguments);
                args.unshift(source);
                return $.validator.format.apply(this, args);
            };
        }
        if (params === undefined) {
            return source;
        }
        if (arguments.length > 2 && params.constructor !== Array) {
            params = $.makeArray(arguments).slice(1);
        }
        if (params.constructor !== Array) {
            params = [params];
        }
        $.each(params, function(i, n) {
            source = source.replace(new RegExp("\\{" + i + "\\}", "g"), function() {
                return n;
            });
        });
        return source;
    };

    $.extend($.validator, {
        defaults: {
            messages: {},
            groups: {},
            rules: {},
            errorClass: "error",
            pendingClass: "pending",
            validClass: "valid",
            errorElement: "label",
            focusCleanup: false,
            focusInvalid: true,
            errorContainer: $([]),
            errorLabelContainer: $([]),
            onsubmit: true,
            ignore: ":hidden",
            ignoreTitle: false,
            onfocusin: function(element) {
                this.lastActive = element;

                // Hide error label and remove error class on focus if enabled
                if (this.settings.focusCleanup) {
                    if (this.settings.unhighlight) {
                        this.settings.unhighlight.call(this, element, this.settings.errorClass, this.settings.validClass);
                    }
                    this.hideThese(this.errorsFor(element));
                }
            },
            onfocusout: function(element) {
                if (!this.checkable(element) && (element.name in this.submitted || !this.optional(element))) {
                    this.element(element);
                }
            },
            onkeyup: function(element, event) {

                // Avoid revalidate the field when pressing one of the following keys
                // Shift       => 16
                // Ctrl        => 17
                // Alt         => 18
                // Caps lock   => 20
                // End         => 35
                // Home        => 36
                // Left arrow  => 37
                // Up arrow    => 38
                // Right arrow => 39
                // Down arrow  => 40
                // Insert      => 45
                // Num lock    => 144
                // AltGr key   => 225
                var excludedKeys = [
                    16, 17, 18, 20, 35, 36, 37,
                    38, 39, 40, 45, 144, 225
                ];

                if (event.which === 9 && this.elementValue(element) === "" || $.inArray(event.keyCode, excludedKeys) !== -1) {
                    return;
                } else if (element.name in this.submitted || element.name in this.invalid) {
                    this.element(element);
                }
            },
            onclick: function(element) {

                // Click on selects, radiobuttons and checkboxes
                if (element.name in this.submitted) {
                    this.element(element);

                    // Or option elements, check parent select in that case
                } else if (element.parentNode.name in this.submitted) {
                    this.element(element.parentNode);
                }
            },
            highlight: function(element, errorClass, validClass) {
                if (element.type === "radio") {
                    this.findByName(element.name).addClass(errorClass).removeClass(validClass);
                } else {
                    $(element).addClass(errorClass).removeClass(validClass);
                }
            },
            unhighlight: function(element, errorClass, validClass) {
                if (element.type === "radio") {
                    this.findByName(element.name).removeClass(errorClass).addClass(validClass);
                } else {
                    $(element).removeClass(errorClass).addClass(validClass);
                }
            }
        },
        // https://jqueryvalidation.org/jQuery.validator.setDefaults/
        setDefaults: function(settings) {
            $.extend($.validator.defaults, settings);
        },
        messages: {
            required: "This field is required.",
            remote: "Please fix this field.",
            email: "Please enter a valid email address.",
            url: "Please enter a valid URL.",
            date: "Please enter a valid date.",
            dateISO: "Please enter a valid date (ISO).",
            number: "Please enter a valid number.",
            digits: "Please enter only digits.",
            equalTo: "Please enter the same value again.",
            maxlength: $.validator.format("Please enter no more than {0} characters."),
            minlength: $.validator.format("Please enter at least {0} characters."),
            rangelength: $.validator.format("Please enter a value between {0} and {1} characters long."),
            range: $.validator.format("Please enter a value between {0} and {1}."),
            max: $.validator.format("Please enter a value less than or equal to {0}."),
            min: $.validator.format("Please enter a value greater than or equal to {0}."),
            step: $.validator.format("Please enter a multiple of {0}.")
        },
        autoCreateRanges: false,
        prototype: {
            init: function() {
                this.labelContainer = $(this.settings.errorLabelContainer);
                this.errorContext = this.labelContainer.length && this.labelContainer || $(this.currentForm);
                this.containers = $(this.settings.errorContainer).add(this.settings.errorLabelContainer);
                this.submitted = {};
                this.valueCache = {};
                this.pendingRequest = 0;
                this.pending = {};
                this.invalid = {};
                this.reset();

                var currentForm = this.currentForm,
                        groups = (this.groups = {}),
                        rules;
                $.each(this.settings.groups, function(key, value) {
                    if (typeof value === "string") {
                        value = value.split(/\s/);
                    }
                    $.each(value, function(index, name) {
                        groups[ name ] = key;
                    });
                });
                rules = this.settings.rules;
                $.each(rules, function(key, value) {
                    rules[ key ] = $.validator.normalizeRule(value);
                });

                function delegate(event) {
                    var isContentEditable = typeof $(this).attr("contenteditable") !== "undefined" && $(this).attr("contenteditable") !== "false";

                    // Set form expando on contenteditable
                    if (!this.form && isContentEditable) {
                        this.form = $(this).closest("form")[ 0 ];
                        this.name = $(this).attr("name");
                    }

                    // Ignore the element if it belongs to another form. This will happen mainly
                    // when setting the `form` attribute of an input to the id of another form.
                    if (currentForm !== this.form) {
                        return;
                    }

                    var validator = $.data(this.form, "validator"),
                            eventType = "on" + event.type.replace(/^validate/, ""),
                            settings = validator.settings;
                    if (settings[ eventType ] && !$(this).is(settings.ignore)) {
                        settings[ eventType ].call(validator, this, event);
                    }
                }

                $(this.currentForm)
                        .on("focusin.validate focusout.validate keyup.validate",
                                ":text, [type='password'], [type='file'], select, textarea, [type='number'], [type='search'], " +
                                "[type='tel'], [type='url'], [type='email'], [type='datetime'], [type='date'], [type='month'], " +
                                "[type='week'], [type='time'], [type='datetime-local'], [type='range'], [type='color'], " +
                                "[type='radio'], [type='checkbox'], [contenteditable], [type='button']", delegate)

                        // Support: Chrome, oldIE
                        // "select" is provided as event.target when clicking a option
                        .on("click.validate", "select, option, [type='radio'], [type='checkbox']", delegate);

                if (this.settings.invalidHandler) {
                    $(this.currentForm).on("invalid-form.validate", this.settings.invalidHandler);
                }
            },
            // https://jqueryvalidation.org/Validator.form/
            form: function() {
                this.checkForm();
                $.extend(this.submitted, this.errorMap);
                this.invalid = $.extend({}, this.errorMap);
                if (!this.valid()) {
                    $(this.currentForm).triggerHandler("invalid-form", [this]);
                }
                this.showErrors();
                return this.valid();
            },
            checkForm: function() {
                this.prepareForm();
                for (var i = 0, elements = (this.currentElements = this.elements()); elements[ i ]; i++) {
                    this.check(elements[ i ]);
                }
                return this.valid();
            },
            // https://jqueryvalidation.org/Validator.element/
            element: function(element) {
                var cleanElement = this.clean(element),
                        checkElement = this.validationTargetFor(cleanElement),
                        v = this,
                        result = true,
                        rs, group;

                if (checkElement === undefined) {
                    delete this.invalid[ cleanElement.name ];
                } else {
                    this.prepareElement(checkElement);
                    this.currentElements = $(checkElement);

                    // If this element is grouped, then validate all group elements already
                    // containing a value
                    group = this.groups[ checkElement.name ];
                    if (group) {
                        $.each(this.groups, function(name, testgroup) {
                            if (testgroup === group && name !== checkElement.name) {
                                cleanElement = v.validationTargetFor(v.clean(v.findByName(name)));
                                if (cleanElement && cleanElement.name in v.invalid) {
                                    v.currentElements.push(cleanElement);
                                    result = v.check(cleanElement) && result;
                                }
                            }
                        });
                    }

                    rs = this.check(checkElement) !== false;
                    result = result && rs;
                    if (rs) {
                        this.invalid[ checkElement.name ] = false;
                    } else {
                        this.invalid[ checkElement.name ] = true;
                    }

                    if (!this.numberOfInvalids()) {

                        // Hide error containers on last error
                        this.toHide = this.toHide.add(this.containers);
                    }
                    this.showErrors();

                    // Add aria-invalid status for screen readers
                    $(element).attr("aria-invalid", !rs);
                }

                return result;
            },
            // https://jqueryvalidation.org/Validator.showErrors/
            showErrors: function(errors) {
                if (errors) {
                    var validator = this;

                    // Add items to error list and map
                    $.extend(this.errorMap, errors);
                    this.errorList = $.map(this.errorMap, function(message, name) {
                        return {
                            message: message,
                            element: validator.findByName(name)[ 0 ]
                        };
                    });

                    // Remove items from success list
                    this.successList = $.grep(this.successList, function(element) {
                        return !(element.name in errors);
                    });
                }
                if (this.settings.showErrors) {
                    this.settings.showErrors.call(this, this.errorMap, this.errorList);
                } else {
                    this.defaultShowErrors();
                }
            },
            // https://jqueryvalidation.org/Validator.resetForm/
            resetForm: function() {
                if ($.fn.resetForm) {
                    $(this.currentForm).resetForm();
                }
                this.invalid = {};
                this.submitted = {};
                this.prepareForm();
                this.hideErrors();
                var elements = this.elements()
                        .removeData("previousValue")
                        .removeAttr("aria-invalid");

                this.resetElements(elements);
            },
            resetElements: function(elements) {
                var i;

                if (this.settings.unhighlight) {
                    for (i = 0; elements[ i ]; i++) {
                        this.settings.unhighlight.call(this, elements[ i ],
                                this.settings.errorClass, "");
                        this.findByName(elements[ i ].name).removeClass(this.settings.validClass);
                    }
                } else {
                    elements
                            .removeClass(this.settings.errorClass)
                            .removeClass(this.settings.validClass);
                }
            },
            numberOfInvalids: function() {
                return this.objectLength(this.invalid);
            },
            objectLength: function(obj) {
                /* jshint unused: false */
                var count = 0,
                        i;
                for (i in obj) {

                    // This check allows counting elements with empty error
                    // message as invalid elements
                    if (obj[ i ] !== undefined && obj[ i ] !== null && obj[ i ] !== false) {
                        count++;
                    }
                }
                return count;
            },
            hideErrors: function() {
                this.hideThese(this.toHide);
            },
            hideThese: function(errors) {
                errors.not(this.containers).text("");
                this.addWrapper(errors).hide();
            },
            valid: function() {
                return this.size() === 0;
            },
            size: function() {
                return this.errorList.length;
            },
            focusInvalid: function() {
                if (this.settings.focusInvalid) {
                    try {
                        $(this.findLastActive() || this.errorList.length && this.errorList[ 0 ].element || [])
                                .filter(":visible")
                                .trigger("focus")

                                // Manually trigger focusin event; without it, focusin handler isn't called, findLastActive won't have anything to find
                                .trigger("focusin");
                    } catch (e) {

                        // Ignore IE throwing errors when focusing hidden elements
                    }
                }
            },
            findLastActive: function() {
                var lastActive = this.lastActive;
                return lastActive && $.grep(this.errorList, function(n) {
                    return n.element.name === lastActive.name;
                }).length === 1 && lastActive;
            },
            elements: function() {
                var validator = this,
                        rulesCache = {};

                // Select all valid inputs inside the form (no submit or reset buttons)
                return $(this.currentForm)
                        .find("input, select, textarea, [contenteditable]")
                        .not(":submit, :reset, :image, :disabled")
                        .not(this.settings.ignore)
                        .filter(function() {
                            var name = this.name || $(this).attr("name"); // For contenteditable
                            var isContentEditable = typeof $(this).attr("contenteditable") !== "undefined" && $(this).attr("contenteditable") !== "false";

                            if (!name && validator.settings.debug && window.console) {
                                console.error("%o has no name assigned", this);
                            }

                            // Set form expando on contenteditable
                            if (isContentEditable) {
                                this.form = $(this).closest("form")[ 0 ];
                                this.name = name;
                            }

                            // Ignore elements that belong to other/nested forms
                            if (this.form !== validator.currentForm) {
                                return false;
                            }

                            // Select only the first element for each name, and only those with rules specified
                            if (name in rulesCache || !validator.objectLength($(this).rules())) {
                                return false;
                            }

                            rulesCache[ name ] = true;
                            return true;
                        });
            },
            clean: function(selector) {
                return $(selector)[ 0 ];
            },
            errors: function() {
                var errorClass = this.settings.errorClass.split(" ").join(".");
                return $(this.settings.errorElement + "." + errorClass, this.errorContext);
            },
            resetInternals: function() {
                this.successList = [];
                this.errorList = [];
                this.errorMap = {};
                this.toShow = $([]);
                this.toHide = $([]);
            },
            reset: function() {
                this.resetInternals();
                this.currentElements = $([]);
            },
            prepareForm: function() {
                this.reset();
                this.toHide = this.errors().add(this.containers);
            },
            prepareElement: function(element) {
                this.reset();
                this.toHide = this.errorsFor(element);
            },
            elementValue: function(element) {
                var $element = $(element),
                        type = element.type,
                        isContentEditable = typeof $element.attr("contenteditable") !== "undefined" && $element.attr("contenteditable") !== "false",
                        val, idx;

                if (type === "radio" || type === "checkbox") {
                    return this.findByName(element.name).filter(":checked").val();
                } else if (type === "number" && typeof element.validity !== "undefined") {
                    return element.validity.badInput ? "NaN" : $element.val();
                }

                if (isContentEditable) {
                    val = $element.text();
                } else {
                    val = $element.val();
                }

                if (type === "file") {

                    // Modern browser (chrome & safari)
                    if (val.substr(0, 12) === "C:\\fakepath\\") {
                        return val.substr(12);
                    }

                    // Legacy browsers
                    // Unix-based path
                    idx = val.lastIndexOf("/");
                    if (idx >= 0) {
                        return val.substr(idx + 1);
                    }

                    // Windows-based path
                    idx = val.lastIndexOf("\\");
                    if (idx >= 0) {
                        return val.substr(idx + 1);
                    }

                    // Just the file name
                    return val;
                }

                if (typeof val === "string") {
                    return val.replace(/\r/g, "");
                }
                return val;
            },
            check: function(element) {
                element = this.validationTargetFor(this.clean(element));

                var rules = $(element).rules(),
                        rulesCount = $.map(rules, function(n, i) {
                            return i;
                        }).length,
                        dependencyMismatch = false,
                        val = this.elementValue(element),
                        result, method, rule, normalizer;

                // Prioritize the local normalizer defined for this element over the global one
                // if the former exists, otherwise user the global one in case it exists.
                if (typeof rules.normalizer === "function") {
                    normalizer = rules.normalizer;
                } else if (typeof this.settings.normalizer === "function") {
                    normalizer = this.settings.normalizer;
                }

                // If normalizer is defined, then call it to retreive the changed value instead
                // of using the real one.
                // Note that `this` in the normalizer is `element`.
                if (normalizer) {
                    val = normalizer.call(element, val);

                    // Delete the normalizer from rules to avoid treating it as a pre-defined method.
                    delete rules.normalizer;
                }

                for (method in rules) {
                    rule = {method: method, parameters: rules[ method ]};
                    try {
                        result = $.validator.methods[ method ].call(this, val, element, rule.parameters);

                        // If a method indicates that the field is optional and therefore valid,
                        // don't mark it as valid when there are no other rules
                        if (result === "dependency-mismatch" && rulesCount === 1) {
                            dependencyMismatch = true;
                            continue;
                        }
                        dependencyMismatch = false;

                        if (result === "pending") {
                            this.toHide = this.toHide.not(this.errorsFor(element));
                            return;
                        }

                        if (!result) {
                            this.formatAndAdd(element, rule);
                            return false;
                        }
                    } catch (e) {
                        if (this.settings.debug && window.console) {
                            console.log("Exception occurred when checking element " + element.id + ", check the '" + rule.method + "' method.", e);
                        }
                        if (e instanceof TypeError) {
                            e.message += ".  Exception occurred when checking element " + element.id + ", check the '" + rule.method + "' method.";
                        }

                        throw e;
                    }
                }
                if (dependencyMismatch) {
                    return;
                }
                if (this.objectLength(rules)) {
                    this.successList.push(element);
                }
                return true;
            },
            // Return the custom message for the given element and validation method
            // specified in the element's HTML5 data attribute
            // return the generic message if present and no method specific message is present
            customDataMessage: function(element, method) {
                return $(element).data("msg" + method.charAt(0).toUpperCase() +
                        method.substring(1).toLowerCase()) || $(element).data("msg");
            },
            // Return the custom message for the given element name and validation method
            customMessage: function(name, method) {
                var m = this.settings.messages[ name ];
                return m && (m.constructor === String ? m : m[ method ]);
            },
            // Return the first defined argument, allowing empty strings
            findDefined: function() {
                for (var i = 0; i < arguments.length; i++) {
                    if (arguments[ i ] !== undefined) {
                        return arguments[ i ];
                    }
                }
                return undefined;
            },
            // The second parameter 'rule' used to be a string, and extended to an object literal
            // of the following form:
            // rule = {
            //     method: "method name",
            //     parameters: "the given method parameters"
            // }
            //
            // The old behavior still supported, kept to maintain backward compatibility with
            // old code, and will be removed in the next major release.
            defaultMessage: function(element, rule) {
                if (typeof rule === "string") {
                    rule = {method: rule};
                }

                var message = this.findDefined(
                        this.customMessage(element.name, rule.method),
                        this.customDataMessage(element, rule.method),
                        // 'title' is never undefined, so handle empty string as undefined
                        !this.settings.ignoreTitle && element.title || undefined,
                        $.validator.messages[ rule.method ],
                        "<strong>Warning: No message defined for " + element.name + "</strong>"
                        ),
                        theregex = /\$?\{(\d+)\}/g;
                if (typeof message === "function") {
                    message = message.call(this, rule.parameters, element);
                } else if (theregex.test(message)) {
                    message = $.validator.format(message.replace(theregex, "{$1}"), rule.parameters);
                }

                return message;
            },
            formatAndAdd: function(element, rule) {
                var message = this.defaultMessage(element, rule);

                this.errorList.push({
                    message: message,
                    element: element,
                    method: rule.method
                });

                this.errorMap[ element.name ] = message;
                this.submitted[ element.name ] = message;
            },
            addWrapper: function(toToggle) {
                if (this.settings.wrapper) {
                    toToggle = toToggle.add(toToggle.parent(this.settings.wrapper));
                }
                return toToggle;
            },
            defaultShowErrors: function() {
                var i, elements, error;
                for (i = 0; this.errorList[ i ]; i++) {
                    error = this.errorList[ i ];
                    if (this.settings.highlight) {
                        this.settings.highlight.call(this, error.element, this.settings.errorClass, this.settings.validClass);
                    }
                    this.showLabel(error.element, error.message);
                }
                if (this.errorList.length) {
                    this.toShow = this.toShow.add(this.containers);
                }
                if (this.settings.success) {
                    for (i = 0; this.successList[ i ]; i++) {
                        this.showLabel(this.successList[ i ]);
                    }
                }
                if (this.settings.unhighlight) {
                    for (i = 0, elements = this.validElements(); elements[ i ]; i++) {
                        this.settings.unhighlight.call(this, elements[ i ], this.settings.errorClass, this.settings.validClass);
                    }
                }
                this.toHide = this.toHide.not(this.toShow);
                this.hideErrors();
                this.addWrapper(this.toShow).show();
            },
            validElements: function() {
                return this.currentElements.not(this.invalidElements());
            },
            invalidElements: function() {
                return $(this.errorList).map(function() {
                    return this.element;
                });
            },
            showLabel: function(element, message) {
                var place, group, errorID, v,
                        error = this.errorsFor(element),
                        elementID = this.idOrName(element),
                        describedBy = $(element).attr("aria-describedby");

                if (error.length) {

                    // Refresh error/success class
                    error.removeClass(this.settings.validClass).addClass(this.settings.errorClass);

                    // Replace message on existing label
                    error.html(message);
                } else {

                    // Create error element
                    error = $("<" + this.settings.errorElement + ">")
                            .attr("id", elementID + "-error")
                            .addClass(this.settings.errorClass)
                            .html(message || "");

                    // Maintain reference to the element to be placed into the DOM
                    place = error;
                    if (this.settings.wrapper) {

                        // Make sure the element is visible, even in IE
                        // actually showing the wrapped element is handled elsewhere
                        place = error.hide().show().wrap("<" + this.settings.wrapper + "/>").parent();
                    }
                    if (this.labelContainer.length) {
                        this.labelContainer.append(place);
                    } else if (this.settings.errorPlacement) {
                        this.settings.errorPlacement.call(this, place, $(element));
                    } else {
                        place.insertAfter(element);
                    }

                    // Link error back to the element
                    if (error.is("label")) {

                        // If the error is a label, then associate using 'for'
                        error.attr("for", elementID);

                        // If the element is not a child of an associated label, then it's necessary
                        // to explicitly apply aria-describedby
                    } else if (error.parents("label[for='" + this.escapeCssMeta(elementID) + "']").length === 0) {
                        errorID = error.attr("id");

                        // Respect existing non-error aria-describedby
                        if (!describedBy) {
                            describedBy = errorID;
                        } else if (!describedBy.match(new RegExp("\\b" + this.escapeCssMeta(errorID) + "\\b"))) {

                            // Add to end of list if not already present
                            describedBy += " " + errorID;
                        }
                        $(element).attr("aria-describedby", describedBy);

                        // If this element is grouped, then assign to all elements in the same group
                        group = this.groups[ element.name ];
                        if (group) {
                            v = this;
                            $.each(v.groups, function(name, testgroup) {
                                if (testgroup === group) {
                                    $("[name='" + v.escapeCssMeta(name) + "']", v.currentForm)
                                            .attr("aria-describedby", error.attr("id"));
                                }
                            });
                        }
                    }
                }
                if (!message && this.settings.success) {
                    error.text("");
                    if (typeof this.settings.success === "string") {
                        error.addClass(this.settings.success);
                    } else {
                        this.settings.success(error, element);
                    }
                }
                this.toShow = this.toShow.add(error);
            },
            errorsFor: function(element) {
                var name = this.escapeCssMeta(this.idOrName(element)),
                        describer = $(element).attr("aria-describedby"),
                        selector = "label[for='" + name + "'], label[for='" + name + "'] *";

                // 'aria-describedby' should directly reference the error element
                if (describer) {
                    selector = selector + ", #" + this.escapeCssMeta(describer)
                            .replace(/\s+/g, ", #");
                }

                return this
                        .errors()
                        .filter(selector);
            },
            // See https://api.jquery.com/category/selectors/, for CSS
            // meta-characters that should be escaped in order to be used with JQuery
            // as a literal part of a name/id or any selector.
            escapeCssMeta: function(string) {
                return string.replace(/([\\!"#$%&'()*+,./:;<=>?@\[\]^`{|}~])/g, "\\$1");
            },
            idOrName: function(element) {
                return this.groups[ element.name ] || (this.checkable(element) ? element.name : element.id || element.name);
            },
            validationTargetFor: function(element) {

                // If radio/checkbox, validate first element in group instead
                if (this.checkable(element)) {
                    element = this.findByName(element.name);
                }

                // Always apply ignore filter
                return $(element).not(this.settings.ignore)[ 0 ];
            },
            checkable: function(element) {
                return (/radio|checkbox/i).test(element.type);
            },
            findByName: function(name) {
                return $(this.currentForm).find("[name='" + this.escapeCssMeta(name) + "']");
            },
            getLength: function(value, element) {
                switch (element.nodeName.toLowerCase()) {
                    case "select":
                        return $("option:selected", element).length;
                    case "input":
                        if (this.checkable(element)) {
                            return this.findByName(element.name).filter(":checked").length;
                        }
                }
                return value.length;
            },
            depend: function(param, element) {
                return this.dependTypes[ typeof param ] ? this.dependTypes[ typeof param ](param, element) : true;
            },
            dependTypes: {
                "boolean": function(param) {
                    return param;
                },
                "string": function(param, element) {
                    return !!$(param, element.form).length;
                },
                "function": function(param, element) {
                    return param(element);
                }
            },
            optional: function(element) {
                var val = this.elementValue(element);
                return !$.validator.methods.required.call(this, val, element) && "dependency-mismatch";
            },
            startRequest: function(element) {
                if (!this.pending[ element.name ]) {
                    this.pendingRequest++;
                    $(element).addClass(this.settings.pendingClass);
                    this.pending[ element.name ] = true;
                }
            },
            stopRequest: function(element, valid) {
                this.pendingRequest--;

                // Sometimes synchronization fails, make sure pendingRequest is never < 0
                if (this.pendingRequest < 0) {
                    this.pendingRequest = 0;
                }
                delete this.pending[ element.name ];
                $(element).removeClass(this.settings.pendingClass);
                if (valid && this.pendingRequest === 0 && this.formSubmitted && this.form()) {
                    $(this.currentForm).submit();

                    // Remove the hidden input that was used as a replacement for the
                    // missing submit button. The hidden input is added by `handle()`
                    // to ensure that the value of the used submit button is passed on
                    // for scripted submits triggered by this method
                    if (this.submitButton) {
                        $("input:hidden[name='" + this.submitButton.name + "']", this.currentForm).remove();
                    }

                    this.formSubmitted = false;
                } else if (!valid && this.pendingRequest === 0 && this.formSubmitted) {
                    $(this.currentForm).triggerHandler("invalid-form", [this]);
                    this.formSubmitted = false;
                }
            },
            previousValue: function(element, method) {
                method = typeof method === "string" && method || "remote";

                return $.data(element, "previousValue") || $.data(element, "previousValue", {
                    old: null,
                    valid: true,
                    message: this.defaultMessage(element, {method: method})
                });
            },
            // Cleans up all forms and elements, removes validator-specific events
            destroy: function() {
                this.resetForm();

                $(this.currentForm)
                        .off(".validate")
                        .removeData("validator")
                        .find(".validate-equalTo-blur")
                        .off(".validate-equalTo")
                        .removeClass("validate-equalTo-blur")
                        .find(".validate-lessThan-blur")
                        .off(".validate-lessThan")
                        .removeClass("validate-lessThan-blur")
                        .find(".validate-lessThanEqual-blur")
                        .off(".validate-lessThanEqual")
                        .removeClass("validate-lessThanEqual-blur")
                        .find(".validate-greaterThanEqual-blur")
                        .off(".validate-greaterThanEqual")
                        .removeClass("validate-greaterThanEqual-blur")
                        .find(".validate-greaterThan-blur")
                        .off(".validate-greaterThan")
                        .removeClass("validate-greaterThan-blur");
            }

        },
        classRuleSettings: {
            required: {required: true},
            email: {email: true},
            url: {url: true},
            date: {date: true},
            dateISO: {dateISO: true},
            number: {number: true},
            digits: {digits: true},
            creditcard: {creditcard: true}
        },
        addClassRules: function(className, rules) {
            if (className.constructor === String) {
                this.classRuleSettings[ className ] = rules;
            } else {
                $.extend(this.classRuleSettings, className);
            }
        },
        classRules: function(element) {
            var rules = {},
                    classes = $(element).attr("class");

            if (classes) {
                $.each(classes.split(" "), function() {
                    if (this in $.validator.classRuleSettings) {
                        $.extend(rules, $.validator.classRuleSettings[ this ]);
                    }
                });
            }
            return rules;
        },
        normalizeAttributeRule: function(rules, type, method, value) {

            // Convert the value to a number for number inputs, and for text for backwards compability
            // allows type="date" and others to be compared as strings
            if (/min|max|step/.test(method) && (type === null || /number|range|text/.test(type))) {
                value = Number(value);

                // Support Opera Mini, which returns NaN for undefined minlength
                if (isNaN(value)) {
                    value = undefined;
                }
            }

            if (value || value === 0) {
                rules[ method ] = value;
            } else if (type === method && type !== "range") {

                // Exception: the jquery validate 'range' method
                // does not test for the html5 'range' type
                rules[ method ] = true;
            }
        },
        attributeRules: function(element) {
            var rules = {},
                    $element = $(element),
                    type = element.getAttribute("type"),
                    method, value;

            for (method in $.validator.methods) {

                // Support for <input required> in both html5 and older browsers
                if (method === "required") {
                    value = element.getAttribute(method);

                    // Some browsers return an empty string for the required attribute
                    // and non-HTML5 browsers might have required="" markup
                    if (value === "") {
                        value = true;
                    }

                    // Force non-HTML5 browsers to return bool
                    value = !!value;
                } else {
                    value = $element.attr(method);
                }

                this.normalizeAttributeRule(rules, type, method, value);
            }

            // 'maxlength' may be returned as -1, 2147483647 ( IE ) and 524288 ( safari ) for text inputs
            if (rules.maxlength && /-1|2147483647|524288/.test(rules.maxlength)) {
                delete rules.maxlength;
            }

            return rules;
        },
        dataRules: function(element) {
            var rules = {},
                    $element = $(element),
                    type = element.getAttribute("type"),
                    method, value;

            for (method in $.validator.methods) {
                value = $element.data("rule" + method.charAt(0).toUpperCase() + method.substring(1).toLowerCase());

                // Cast empty attributes like `data-rule-required` to `true`
                if (value === "") {
                    value = true;
                }

                this.normalizeAttributeRule(rules, type, method, value);
            }
            return rules;
        },
        staticRules: function(element) {
            var rules = {},
                    validator = $.data(element.form, "validator");

            if (validator.settings.rules) {
                rules = $.validator.normalizeRule(validator.settings.rules[ element.name ]) || {};
            }
            return rules;
        },
        normalizeRules: function(rules, element) {

            // Handle dependency check
            $.each(rules, function(prop, val) {

                // Ignore rule when param is explicitly false, eg. required:false
                if (val === false) {
                    delete rules[ prop ];
                    return;
                }
                if (val.param || val.depends) {
                    var keepRule = true;
                    switch (typeof val.depends) {
                        case "string":
                            keepRule = !!$(val.depends, element.form).length;
                            break;
                        case "function":
                            keepRule = val.depends.call(element, element);
                            break;
                    }
                    if (keepRule) {
                        rules[ prop ] = val.param !== undefined ? val.param : true;
                    } else {
                        $.data(element.form, "validator").resetElements($(element));
                        delete rules[ prop ];
                    }
                }
            });

            // Evaluate parameters
            $.each(rules, function(rule, parameter) {
                rules[ rule ] = $.isFunction(parameter) && rule !== "normalizer" ? parameter(element) : parameter;
            });

            // Clean number parameters
            $.each(["minlength", "maxlength"], function() {
                if (rules[ this ]) {
                    rules[ this ] = Number(rules[ this ]);
                }
            });
            $.each(["rangelength", "range"], function() {
                var parts;
                if (rules[ this ]) {
                    if ($.isArray(rules[ this ])) {
                        rules[ this ] = [Number(rules[ this ][ 0 ]), Number(rules[ this ][ 1 ])];
                    } else if (typeof rules[ this ] === "string") {
                        parts = rules[ this ].replace(/[\[\]]/g, "").split(/[\s,]+/);
                        rules[ this ] = [Number(parts[ 0 ]), Number(parts[ 1 ])];
                    }
                }
            });

            if ($.validator.autoCreateRanges) {

                // Auto-create ranges
                if (rules.min != null && rules.max != null) {
                    rules.range = [rules.min, rules.max];
                    delete rules.min;
                    delete rules.max;
                }
                if (rules.minlength != null && rules.maxlength != null) {
                    rules.rangelength = [rules.minlength, rules.maxlength];
                    delete rules.minlength;
                    delete rules.maxlength;
                }
            }

            return rules;
        },
        // Converts a simple string to a {string: true} rule, e.g., "required" to {required:true}
        normalizeRule: function(data) {
            if (typeof data === "string") {
                var transformed = {};
                $.each(data.split(/\s/), function() {
                    transformed[ this ] = true;
                });
                data = transformed;
            }
            return data;
        },
        // https://jqueryvalidation.org/jQuery.validator.addMethod/
        addMethod: function(name, method, message) {
            $.validator.methods[ name ] = method;
            $.validator.messages[ name ] = message !== undefined ? message : $.validator.messages[ name ];
            if (method.length < 3) {
                $.validator.addClassRules(name, $.validator.normalizeRule(name));
            }
        },
        // https://jqueryvalidation.org/jQuery.validator.methods/
        methods: {
            // https://jqueryvalidation.org/required-method/
            required: function(value, element, param) {

                // Check if dependency is met
                if (!this.depend(param, element)) {
                    return "dependency-mismatch";
                }
                if (element.nodeName.toLowerCase() === "select") {

                    // Could be an array for select-multiple or a string, both are fine this way
                    var val = $(element).val();
                    return val && val.length > 0;
                }
                if (this.checkable(element)) {
                    return this.getLength(value, element) > 0;
                }
                return value !== undefined && value !== null && value.length > 0;
            },
            // https://jqueryvalidation.org/email-method/
            email: function(value, element) {

                // From https://html.spec.whatwg.org/multipage/forms.html#valid-e-mail-address
                // Retrieved 2014-01-14
                // If you have a problem with this implementation, report a bug against the above spec
                // Or use custom methods to implement your own email validation
                return this.optional(element) || /^[a-zA-Z0-9.!#$%&'*+\/=?^_`{|}~-]+@[a-zA-Z0-9](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?(?:\.[a-zA-Z0-9](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?)*$/.test(value);
            },
            // https://jqueryvalidation.org/url-method/
            url: function(value, element) {

                // Copyright (c) 2010-2013 Diego Perini, MIT licensed
                // https://gist.github.com/dperini/729294
                // see also https://mathiasbynens.be/demo/url-regex
                // modified to allow protocol-relative URLs
                return this.optional(element) || /^(?:(?:(?:https?|ftp):)?\/\/)(?:\S+(?::\S*)?@)?(?:(?!(?:10|127)(?:\.\d{1,3}){3})(?!(?:169\.254|192\.168)(?:\.\d{1,3}){2})(?!172\.(?:1[6-9]|2\d|3[0-1])(?:\.\d{1,3}){2})(?:[1-9]\d?|1\d\d|2[01]\d|22[0-3])(?:\.(?:1?\d{1,2}|2[0-4]\d|25[0-5])){2}(?:\.(?:[1-9]\d?|1\d\d|2[0-4]\d|25[0-4]))|(?:(?:[a-z\u00a1-\uffff0-9]-*)*[a-z\u00a1-\uffff0-9]+)(?:\.(?:[a-z\u00a1-\uffff0-9]-*)*[a-z\u00a1-\uffff0-9]+)*(?:\.(?:[a-z\u00a1-\uffff]{2,})).?)(?::\d{2,5})?(?:[/?#]\S*)?$/i.test(value);
            },
            // https://jqueryvalidation.org/date-method/
            date: (function() {
                var called = false;

                return function(value, element) {
                    if (!called) {
                        called = true;
                        if (this.settings.debug && window.console) {
                            console.warn(
                                    "The `date` method is deprecated and will be removed in version '2.0.0'.\n" +
                                    "Please don't use it, since it relies on the Date constructor, which\n" +
                                    "behaves very differently across browsers and locales. Use `dateISO`\n" +
                                    "instead or one of the locale specific methods in `localizations/`\n" +
                                    "and `additional-methods.js`."
                                    );
                        }
                    }

                    return this.optional(element) || !/Invalid|NaN/.test(new Date(value).toString());
                };
            }()),
            // https://jqueryvalidation.org/dateISO-method/
            dateISO: function(value, element) {
                return this.optional(element) || /^\d{4}[\/\-](0?[1-9]|1[012])[\/\-](0?[1-9]|[12][0-9]|3[01])$/.test(value);
            },
            // https://jqueryvalidation.org/number-method/
            number: function(value, element) {
                return this.optional(element) || /^(?:-?\d+|-?\d{1,3}(?:,\d{3})+)?(?:\.\d+)?$/.test(value);
            },
            // https://jqueryvalidation.org/digits-method/
            digits: function(value, element) {
                return this.optional(element) || /^\d+$/.test(value);
            },
            // https://jqueryvalidation.org/minlength-method/
            minlength: function(value, element, param) {
                var length = $.isArray(value) ? value.length : this.getLength(value, element);
                return this.optional(element) || length >= param;
            },
            // https://jqueryvalidation.org/maxlength-method/
            maxlength: function(value, element, param) {
                var length = $.isArray(value) ? value.length : this.getLength(value, element);
                return this.optional(element) || length <= param;
            },
            // https://jqueryvalidation.org/rangelength-method/
            rangelength: function(value, element, param) {
                var length = $.isArray(value) ? value.length : this.getLength(value, element);
                return this.optional(element) || (length >= param[ 0 ] && length <= param[ 1 ]);
            },
            // https://jqueryvalidation.org/min-method/
            min: function(value, element, param) {
                return this.optional(element) || value >= param;
            },
            // https://jqueryvalidation.org/max-method/
            max: function(value, element, param) {
                return this.optional(element) || value <= param;
            },
            // https://jqueryvalidation.org/range-method/
            range: function(value, element, param) {
                return this.optional(element) || (value >= param[ 0 ] && value <= param[ 1 ]);
            },
            // https://jqueryvalidation.org/step-method/
            step: function(value, element, param) {
                var type = $(element).attr("type"),
                        errorMessage = "Step attribute on input type " + type + " is not supported.",
                        supportedTypes = ["text", "number", "range"],
                        re = new RegExp("\\b" + type + "\\b"),
                        notSupported = type && !re.test(supportedTypes.join()),
                        decimalPlaces = function(num) {
                            var match = ("" + num).match(/(?:\.(\d+))?$/);
                            if (!match) {
                                return 0;
                            }

                            // Number of digits right of decimal point.
                            return match[ 1 ] ? match[ 1 ].length : 0;
                        },
                        toInt = function(num) {
                            return Math.round(num * Math.pow(10, decimals));
                        },
                        valid = true,
                        decimals;

                // Works only for text, number and range input types
                // TODO find a way to support input types date, datetime, datetime-local, month, time and week
                if (notSupported) {
                    throw new Error(errorMessage);
                }

                decimals = decimalPlaces(param);

                // Value can't have too many decimals
                if (decimalPlaces(value) > decimals || toInt(value) % toInt(param) !== 0) {
                    valid = false;
                }

                return this.optional(element) || valid;
            },
            // https://jqueryvalidation.org/equalTo-method/
            equalTo: function(value, element, param) {

                // Bind to the blur event of the target in order to revalidate whenever the target field is updated
                var target = $(param);
                if (this.settings.onfocusout && target.not(".validate-equalTo-blur").length) {
                    target.addClass("validate-equalTo-blur").on("blur.validate-equalTo", function() {
                        $(element).valid();
                    });
                }
                return value === target.val();
            },
            // https://jqueryvalidation.org/remote-method/
            remote: function(value, element, param, method) {
                if (this.optional(element)) {
                    return "dependency-mismatch";
                }

                method = typeof method === "string" && method || "remote";

                var previous = this.previousValue(element, method),
                        validator, data, optionDataString;

                if (!this.settings.messages[ element.name ]) {
                    this.settings.messages[ element.name ] = {};
                }
                previous.originalMessage = previous.originalMessage || this.settings.messages[ element.name ][ method ];
                this.settings.messages[ element.name ][ method ] = previous.message;

                param = typeof param === "string" && {url: param} || param;
                optionDataString = $.param($.extend({data: value}, param.data));
                if (previous.old === optionDataString) {
                    return previous.valid;
                }

                previous.old = optionDataString;
                validator = this;
                this.startRequest(element);
                data = {};
                data[ element.name ] = value;
                $.ajax($.extend(true, {
                    mode: "abort",
                    port: "validate" + element.name,
                    dataType: "json",
                    data: data,
                    context: validator.currentForm,
                    success: function(response) {
                        var valid = response === true || response === "true",
                                errors, message, submitted;

                        validator.settings.messages[ element.name ][ method ] = previous.originalMessage;
                        if (valid) {
                            submitted = validator.formSubmitted;
                            validator.resetInternals();
                            validator.toHide = validator.errorsFor(element);
                            validator.formSubmitted = submitted;
                            validator.successList.push(element);
                            validator.invalid[ element.name ] = false;
                            validator.showErrors();
                        } else {
                            errors = {};
                            message = response || validator.defaultMessage(element, {method: method, parameters: value});
                            errors[ element.name ] = previous.message = message;
                            validator.invalid[ element.name ] = true;
                            validator.showErrors(errors);
                        }
                        previous.valid = valid;
                        validator.stopRequest(element, valid);
                    }
                }, param));
                return "pending";
            }
        }

    });

// Ajax mode: abort
// usage: $.ajax({ mode: "abort"[, port: "uniqueport"]});
// if mode:"abort" is used, the previous request on that port (port can be undefined) is aborted via XMLHttpRequest.abort()

    var pendingRequests = {},
            ajax;

// Use a prefilter if available (1.5+)
    if ($.ajaxPrefilter) {
        $.ajaxPrefilter(function(settings, _, xhr) {
            var port = settings.port;
            if (settings.mode === "abort") {
                if (pendingRequests[ port ]) {
                    pendingRequests[ port ].abort();
                }
                pendingRequests[ port ] = xhr;
            }
        });
    } else {

        // Proxy ajax
        ajax = $.ajax;
        $.ajax = function(settings) {
            var mode = ("mode" in settings ? settings : $.ajaxSettings).mode,
                    port = ("port" in settings ? settings : $.ajaxSettings).port;
            if (mode === "abort") {
                if (pendingRequests[ port ]) {
                    pendingRequests[ port ].abort();
                }
                pendingRequests[ port ] = ajax.apply(this, arguments);
                return pendingRequests[ port ];
            }
            return ajax.apply(this, arguments);
        };
    }
    return $;
}));


main.js

$.validator.setDefaults({
    submitHandler: function() {
        alert("submitted!");
        /// use ajax to to send data
    }
});

$().ready(function() {
    $("#signupForm").validate({
        rules: {
            firstname: "required",
            lastname: "required",
            username: {
                required: true,
                minlength: 2
            },
            password: {
                required: true,
                minlength: 5
            },
            confirm_password: {
                required: true,
                minlength: 5,
                equalTo: "#password"
            },
            email: {
                required: true,
                email: true
            },
            topic: {
                required: "#newsletter:checked",
                minlength: 2
            },
            agree: "required"
        },
        messages: {
            firstname: "Please enter your firstname",
            lastname: "Please enter your lastname",
            username: {
                required: "Please enter a username",
                minlength: "Your username must consist of at least 2 characters"
            },
            password: {
                required: "Please provide a password",
                minlength: "Your password must be at least 5 characters long"
            },
            confirm_password: {
                required: "Please provide a password",
                minlength: "Your password must be at least 5 characters long",
                equalTo: "Please enter the same password as above"
            },
            email: "Please enter a valid email address",
            agree: "Please accept our policy",
            topic: "Please select at least 2 topics"
        }
    });

    // propose username by combining first- and lastname
    $("#username").focus(function() {
        var firstname = $("#firstname").val();
        var lastname = $("#lastname").val();
        if (firstname && lastname && !this.value) {
            this.value = firstname + "." + lastname;
        }
    });

    //code to hide topic selection, disable for demo
    var newsletter = $("#newsletter");
    // newsletter topics are optional, hide at first
    var inital = newsletter.is(":checked");
    var topics = $("#newsletter_topics")[inital ? "removeClass" : "addClass"]("gray");
    var topicInputs = topics.find("input").attr("disabled", !inital);
    // show when newsletter is checked
    newsletter.click(function() {
        topics[this.checked ? "removeClass" : "addClass"]("gray");
        topicInputs.attr("disabled", !this.checked);
    });
});

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