JavaScript for...in Loop Guide

for…in Loop – Iterates over **enumerable keys** of an object. Always verify ownership with `Object.hasOwn()` to skip inherited props.

👉 Syntax

for (const key in object) {
  if (Object.hasOwn(object, key)) {
    // key = property name
  }
}

🧪 Example

const user = { name: 'Ada', age: 30 };
for (const k in user) {
  console.log(`${k}: ${user[k]}`);
}