How to Use Strict Mode in JavaScript to Achieve Desired Results?

In JavaScript, strict mode can help you achieve desired results by preventing certain unsafe actions and coding mistakes. Here are a few examples:

1. Preventing variable declaration errors: Strict mode requires you to declare all variables with var, let, or const before using them. This helps prevent accidental global variable declaration.

"use strict";
x = 10; // Throws an error: x is not defined
let x = 10; // Correct

2. Preventing property assignment to read-only properties: In strict mode, attempting to assign a value to a read-only property of an object will throw an error.

"use strict";
const obj = {};
Object.defineProperty(obj, "x", {value: 42, writable: false});
obj.x = 10; // Throws an error: Cannot assign to read only property 'x' of object '#<Object>'

3. Preventing accidental deletion of variables: In strict mode, attempting to delete a variable or function will throw an error.

"use strict";
let x = 10;
delete x; // Throws an error: Deleting local variable in strict mode

4. Preventing duplicated property names in an object literal: In strict mode, attempting to create an object literal with duplicate property names will throw an error.

"use strict";
let obj = {x: 10, x: 20}; // Throws an error: Duplicate data property in object literal not allowed in strict mode

By using strict mode, you can enforce a safer and more consistent coding style, and reduce the likelihood of introducing bugs and security vulnerabilities into your code.