JavaScript Hoisting

What is Hoisting?

Hoisting moves declarations to the top of scope.

console.log(x); // undefined (not error!)
var x = 5;

JavaScript sees it as:

var x;
console.log(x);
x = 5;

let/const Hoisting

console.log(x); // Error! (Temporal Dead Zone)
let x = 5;

let/const are hoisted but not initialized.

Key Takeaway

var hoists and initializes. let/const hoist but not initialize. Always declare before use.