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JavaScript

JavaScript Hoisting

JavaScript hoisting moves variable and function declarations to the top.

Read Time

5 min read

Difficulty

Beginner

Last Updated

Jun 15, 2026

Version

v1.0.0

Introduction

JavaScript secretly moves all variable and function declarations to the very top of the script before running the code. Because of this strange behavior, developers can call a function on line 1 even if the function isn't written until line 50.

Example

1/* this shows hoisting */
2x = 5;
3console.log(x);
4var x; // Declaration is hoisted

Key Points

Hoisting moves declarations, not assignments.
`var` declarations hoist and initialize as undefined.
`let` and `const` declarations hoist but do not initialize.
Calling functions before they are written works perfectly.

Up Next

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Go to JS Closures ❯