JavaScript's use strict

JavaScript's use strict is a directive that indicates to the JavaScript engine to interpret the code in strict mode. This means that the code will be executed in a more secure and error-free manner.

In strict mode, certain practices that were allowed in normal JavaScript will cause an error. This can help catch mistakes early in the development process and prevent security vulnerabilities.

Here are some of the benefits of using "use strict" in JavaScript:

  1. Prevent global variables: In strict mode, implicit creation of global variables is disallowed. This means that if you forget to use the "var" keyword, an error will be thrown.

  2. Improved error handling: In strict mode, many types of errors will result in a thrown exception, rather than just being silently ignored. This can help you identify bugs more easily.

  3. Improved security: Strict mode disallows dangerous practices like modifying read-only properties and accessing the object's prototype. This helps to prevent security vulnerabilities.

  4. Improved performance: Strict mode can also result in faster performance, since the JavaScript engine does not have to check for certain errors that are disallowed in strict mode.

To enable strict mode in JavaScript, you simply add use strict at the beginning of your code, or at the beginning of a function. For example:

1"use strict";
2// your code here

or

1function myFunction() {
2  "use strict";
3  // your code here
4}

Using "use strict" in JavaScript can help improve the security, error handling, and performance of your code.

1myFunction();
2let a = 5
3function  myFunction()  {
4	"use strict";
5	console.log("Inside myFunction"); // Output: Inside myFunction
6	a = 10; // Error: Uncaught ReferenceError: y is not defined
7}