🔁 JavaScript Object Loops

Last Updated: 15th October 2025

Objects store data in key-value pairs, but unlike arrays, you can’t use normal for or forEach() directly.

So we use special object loop techniques to read, display, or process data.

Hinglish Tip 🗣: Object loop ka kaam hai — “har ek key aur value ko ghoom ghoom kar dekhna”.

1. for...in Loop (Most Common)

Used to iterate over keys (property names) of an object.

const user = {
  name: "Riya",
  age: 25,
  city: "Delhi",
};

for (let key in user) {
  console.log(key); // prints keys
  console.log(user[key]); // prints values
}

Hinglish Tip 🗣: for...in loop keys par chalta hai, values nikalne ke liye user[key] likhna padta hai.

2. Loop Using Object.keys()

  • Returns an array of keys.
  • You can use for...of or forEach() on it.
const person = { name: "Amit", job: "Designer", age: 28 };

for (let key of Object.keys(person)) {
  console.log(`${key}: ${person[key]}`);
}

const car = { brand: "Tata", model: "Nexon", year: 2024 };

const keys = Object.keys(car); // ['brand', 'model', 'year']

for (let i = 0; i < keys.length; i++) {
  console.log(keys[i], "→", car[keys[i]]);
}

3. Loop Using Object.values()

  • Returns an array of values.
  • Helpful when you only need values (not keys).
const product = { name: "Phone", price: 15000, brand: "Mi" };

for (let value of Object.values(product)) {
  console.log(value);
}

const product = { name: "Phone", price: 15000, brand: "Mi" };

const values = Object.values(product);

for (let i = 0; i < values.length; i++) {
  console.log(values[i]);
}

4. Loop Using Object.entries()

  • Returns an array of [key, value] pairs.
  • You can use array destructuring to easily access both.
const book = { title: "Gita", author: "Ved Vyasa", year: "Ancient" };

for (let [key, value] of Object.entries(book)) {
  console.log(`${key}: ${value}`);
}

const book = { title: "Gita", author: "Ved Vyasa", year: "Ancient" };

const entries = Object.entries(book);

for (let i = 0; i < entries.length; i++) {
  const key = entries[i][0];
  const value = entries[i][1];
  console.log(`${key}: ${value}`);
}

💡 Quick Practice

  • Create an object student = name: "Karan", marks: 89, grade: "A"
  • Print all keys using for...in
  • Print both keys and values using Object.keys()
  • Print only values using Object.values()
  • Print key–value pairs using Object.entries()
  • Exercise Set 1
  • Exercise Set 2
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