React Form Validation Tutorial Example

Hello Devs, 

In this tutorial, we will learn React Form Validation Tutorial Example

Form validation is a primary part of any application. we always require to add input validation when we are adding form in our application. There is a some simple validation like require, email, phone number, only number validation is almost we need to add.

Follow this step by step guide below. 

Step 1: Install React App

npx create-react-app my-app

Step 2: Create DemoForm Component

src/DemoForm.js

import React from 'react';
  
class DemoForm extends React.Component {
    constructor() {
    super();
    this.state = {
      input: {},
      errors: {}
    };
     
    this.handleChange = this.handleChange.bind(this);
    this.handleSubmit = this.handleSubmit.bind(this);
  }
     
  handleChange(event) {
    let input = this.state.input;
    input[event.target.name] = event.target.value;
  
    this.setState({
      input
    });
  }
    
  handleSubmit(event) {
    event.preventDefault();
  
    if(this.validate()){
        console.log(this.state);
  
        let input = {};
        input["name"] = "";
        input["email"] = "";
        input["comment"] = "";
        this.setState({input:input});
  
        alert('Demo Form is submited');
    }
  }
  
  validate(){
      let input = this.state.input;
      let errors = {};
      let isValid = true;
  
      if (!input["name"]) {
        isValid = false;
        errors["name"] = "Please enter your name.";
      }
  
      if (!input["email"]) {
        isValid = false;
        errors["email"] = "Please enter your email Address.";
      }
  
      if (typeof input["email"] !== "undefined") {
          
        var pattern = new RegExp(/^(("[\w-\s]+")|([\w-]+(?:\.[\w-]+)*)|("[\w-\s]+")([\w-]+(?:\.[\w-]+)*))(@((?:[\w-]+\.)*\w[\w-]{0,66})\.([a-z]{2,6}(?:\.[a-z]{2})?)$)|(@\[?((25[0-5]\.|2[0-4][0-9]\.|1[0-9]{2}\.|[0-9]{1,2}\.))((25[0-5]|2[0-4][0-9]|1[0-9]{2}|[0-9]{1,2})\.){2}(25[0-5]|2[0-4][0-9]|1[0-9]{2}|[0-9]{1,2})\]?$)/i);
        if (!pattern.test(input["email"])) {
          isValid = false;
          errors["email"] = "Please enter valid email address.";
        }
      }
  
      if (!input["comment"]) {
        isValid = false;
        errors["comment"] = "Please enter your comment.";
      }
  
      this.setState({
        errors: errors
      });
  
      return isValid;
  }
     
  render() {
    return (
      <div>
        <h1>React Form Validation Example - rathorji.in</h1>
        <form onSubmit={this.handleSubmit}>
  
          <div class="form-group">
            <label for="name">Name:</label>
            <input 
              type="text" 
              name="name" 
              value={this.state.input.name}
              onChange={this.handleChange}
              class="form-control" 
              placeholder="Enter name" 
              id="name" />
  
              <div className="text-danger">{this.state.errors.name}</div>
          </div>
  
          <div class="form-group">
            <label for="email">Email Address:</label>
            <input 
              type="text" 
              name="email" 
              value={this.state.input.email}
              onChange={this.handleChange}
              class="form-control" 
              placeholder="Enter email" 
              id="email" />
   
              <div className="text-danger">{this.state.errors.email}</div>
          </div>
  
          <div class="form-group">
            <label for="comment">Comment:</label>
            <textarea 
              name="comment"
              value={this.state.input.comment} 
              onChange={this.handleChange}
              placeholder="Enter comment"
              class="form-control" />
  
              <div className="text-danger">{this.state.errors.comment}</div>
          </div>
             
          <input type="submit" value="Submit" class="btn btn-success" />
        </form>
      </div>
    );
  }
}
  
export default DemoForm;

Step 3: Import Component

src/index.js

import React from 'react';
import ReactDOM from 'react-dom';
import * as serviceWorker from './serviceWorker';
import 'bootstrap/dist/css/bootstrap.min.css';
  
import DemoForm from './DemoForm';
  
ReactDOM.render(
  <React.StrictMode>
    <div className="container">
       <DemoForm />
    </div>
  </React.StrictMode>,
  document.getElementById('root')
);
  
serviceWorker.unregister();

Run this below command: 

npm start

Open this URL: 

http://localhost:3000

May this example help you.