JavaScript Hoisting

JavaScript hoisting is a behavior where variable and function declarations are moved to the top of their containing scope during the compilation phase, before the code is executed.

JavaScript Declarations are Hoisted

In JavaScript, a variable can be declared after it has been used.

Example

x = 5; // Assign 5 to x

elem = document.getElementById("demo"); // Find an element
elem.innerHTML = x;                     // Display x in the element

var x; // Declare x

The let and const Keywords

Variables declared using let and const are hoisted to the top of their block scope, but they are not initialized until their declaration is evaluated.

Example

console.log(myVar); // ReferenceError: Cannot access 'myVar' before initialization
let myVar = 10;

JavaScript Initializations are Not Hoisted

JavaScript only hoists declarations, not initializations.

Example

console.log(myVar); // Output: undefined
var myVar = 10;