Explanation of JavaScript's for...in and for...of Loops

Faisal Nawaz — Wed, 26 Mar 2025 10:27:41 +0000

Hey everyone,

I’m Faisal Nawaz, a frontend developer with over 10 years of experience. I’m honored to contribute to this article.

for...in Loop

The for...in loop iterates over the enumerable properties (keys/indexes) of an object or array.

Example:

const fruits = ['Mango', 'Apple', 'Banana', 'Orange'];

for (const item in fruits) {
console.log(item);
}

// Output: 0, 1, 2, 3

The for...of loop extracts the actual values of iterable objects (like arrays).

for (const item of fruits) {
console.log(item);
}

// Output: Mango, Apple, Banana, Orange

Key Difference
for...in → Returns keys/indexes
for...of → Returns values

This distinction helps in choosing the right loop for different use cases in JavaScript.