🧰 JavaScript Object Methods

Last Updated: 15th October 2025

Object methods are built-in functions that help you work with objects —
like finding keys, values, merging, freezing, or copying objects.

Hinglish Tip 🗣: Object methods aise tools hain jo object ke andar ka data samajhne, badalne, ya copy karne me help karte hain.

🗂 Commonly Used Object Methods

MethodDescription
Object.keys()Returns an array of all keys
Object.values()Returns an array of all values
Object.entries()Returns an array of [key, value] pairs
Object.assign()Copies properties from one object to another
Object.freeze()Makes an object read-only (can’t be changed)
Object.seal()Prevents adding/removing properties (but can update values)
Object.hasOwn()Checks if a key exists in object

✏ Example

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

console.log(Object.keys(user)); // ["name", "age", "city"]
console.log(Object.values(user)); // ["Riya", 25, "Delhi"]
console.log(Object.entries(user)); // [["name", "Riya"], ["age", 25], ["city", "Delhi"]]

const target = { a: 1 };
const source = { b: 2, c: 3 };
const merged = Object.assign(target, source);
console.log(merged); // { a: 1, b: 2, c: 3 }

Object.freeze(user);
user.age = 30; // ❌ will not change
console.log(user.age); // 25

Object.seal(user);
user.age = 30; // ❌ will not change
user.city = "Mumbai";
console.log(user.age); // 25

console.log(Object.hasOwn(user, "name")); // true

⚡ Mini Notes

  • 🔒 freeze() → nothing can be changed.
  • 🔐 seal() → no new keys, no delete, but update allowed.
  • 🔍 hasOwn() → better than hasOwnProperty() in modern JS (ES2022).

💡 Quick Practice

  • Create an object car with brand, model, price.
  • Use Object.keys() and Object.values() to print details.
  • Use Object.assign() to merge it with another object color: "red".
  • Use Object.freeze() and try to change one value.
  • Use Object.hasOwn(car, "model") to verify key presence.
  • Exercise Set 1
  • Exercise Set 2
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