TypeScript is a superset of JavaScript which means it extends JavaScript with additional features. TypeScript introduces a concept called "strict mode" which helps to catch some common errors at the compile-time. In this tutorial, we will learn about strict mode in TypeScript and how to use it in our code.


What is Strict Mode in TypeScript?

Strict mode in TypeScript is a set of rules and constraints that a TypeScript program must follow. When we enable strict mode in TypeScript, it enables several type-checking features that help catch common programming errors. These errors would typically go unnoticed in JavaScript, and we would only find out about them at runtime.


Enabling Strict Mode in TypeScript

We can enable strict mode in TypeScript by adding the "strict" flag in the tsconfig.json file. Here's how to do it: 

{
  "compilerOptions": {
    "strict": true
  }
}


The "strict" flag is a combination of several individual flags that we can set. For example, the "noImplicitAny" flag tells TypeScript to issue an error when it can't determine the type of a variable.


TypeScript's Strict Mode Features

Here are some of the features that TypeScript's strict mode enables:

  1. noImplicitAny: This flag tells TypeScript to issue an error when it can't determine the type of a variable.
  2. strictNullChecks: This flag tells TypeScript to issue an error when we try to use a variable that may be null or undefined.
  3. strictFunctionTypes: This flag tells TypeScript to issue an error when we try to use a function that doesn't match the expected type.
  4. strictPropertyInitialization: This flag tells TypeScript to issue an error when we try to use a variable that hasn't been initialized.
  5. noUnusedLocals: This flag tells TypeScript to issue an error when we declare a variable that we don't use.
  6. noUnusedParameters: This flag tells TypeScript to issue an error when we declare a parameter that we don't use.
  7. alwaysStrict: This flag tells TypeScript to always emit "use strict" in the output JavaScript code.



Benefits of Strict Mode in TypeScript

Enabling strict mode in TypeScript brings several benefits:

  1. Catching errors at compile-time: With strict mode enabled, we can catch some common errors before we even run the code.
  2. Writing safer code: With stricter type checking, we can write code that is less likely to fail at runtime.
  3. Improved readability: Strict mode flags encourage us to write code that is more explicit and easier to read.



Conclusion

In conclusion, TypeScript's strict mode is a powerful tool that helps us catch common errors at compile-time. By enabling strict mode, we can write safer code, catch errors early, and improve the readability of our code. If you're working on a TypeScript project, I strongly recommend enabling strict mode to take advantage of these benefits.