Hoisting in JavaScript

Hoisting in JavaScript

Moving the declaration of variable and function at the top is called Hoisting.

First function declaration is hoisted and then variable declaration is hoisted.

Example 1

	console.log(a); // undefined
	var a = 10;
	console.log(a); // 10

view raw gistfile1.js hosted with ❤ by GitHub

In the above program JavaScript compiler moves declaration of variable at the top.

	var a;
	console.log(a); // undefined
	a = 10;
	console.log(a); // 10

view raw gistfile1.js hosted with ❤ by GitHub

Example 2

	console.log(a); // undefined
	var a = 10;
	console.log(a); // 10
	greet(); // "Hello"
	function greet() {
	console.log("Hello");
	}

view raw gistfile1.js hosted with ❤ by GitHub

In the above program JavaScript compiler moves declaration of variable and function at the top.

	function greet() {
	console.log("Hello");
	}
	var a;
	console.log(a); // undefined
	a = 10;
	console.log(a); // 10
	greet(); // "Hello"

view raw gistfile1.js hosted with ❤ by GitHub