Lecture 165:- More on Strict Mode

Strict Mode is a feature in JavaScript that was introduced in ECMAScript 5. It is a way to opt-in to a restricted version of JavaScript, which helps to avoid common mistakes and make code more robust. When you enable strict mode in your code, the JavaScript engine will enforce stricter parsing and error handling rules.

Some of the things that strict mode enforces include:

• It prevents the use of undeclared variables. In non-strict mode, this would simply create a new global variable, which can cause unexpected behavior and hard-to-find bugs.
• It disallows assignments to non-writable properties, and throws a TypeError when you try to modify non-configurable properties or delete non-deletable properties.
• It prohibits the use of octal literals, which can lead to confusing code.
• It throws an error when you try to delete a variable, function, or argument.
• It prevents duplicate property names in object literals.
• It makes this keyword inside functions undefined, rather than referring to the global object.

Strict mode can be enabled in two ways:

1. Globally, by adding the following line of code at the beginning of your JavaScript file or script tag:

   javascriptCopy code

   'use strict';

2. Locally, by adding the same line of code inside a function, which enables strict mode only for that function and any functions nested inside it.

Using strict mode is a good practice to adopt in your JavaScript projects, as it helps to avoid common mistakes and improve the overall quality of your code.