JavaScript Object Methods

• Object.keys(obj) - Returns an array of an object's keys

  const obj = { name: "John", age: 30 };
  console.log(Object.keys(obj)); // ["name", "age"]

• Object.values(obj) - Returns an array of an object's values

  console.log(Object.values(obj)); // ["John", 30]

• Object.entries(obj) - Returns an array of key-value pairs

  console.log(Object.entries(obj)); // [["name", "John"], ["age", 30]]

• Object.assign(target, source) - Copies properties from one object to another

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

• Object.freeze(obj) - Freezes an object (prevents modification)

  const obj2 = { name: "Alice" };
  Object.freeze(obj2);
  obj2.name = "Bob"; // No effect
  console.log(obj2.name); // "Alice"

• Object.seal(obj) - Prevents adding/removing properties but allows modification

  const obj3 = { age: 25 };
  Object.seal(obj3);
  obj3.age = 26; // Allowed
  delete obj3.age; // Not allowed
  console.log(obj3); // { age: 26 }

• Object.create(proto) - Creates a new object with a specified prototype

  const parent = { greet: function() { return "Hello"; } };
  const child = Object.create(parent);
  console.log(child.greet()); // "Hello"

• Object.getPrototypeOf(obj) - Returns the prototype of an object

  console.log(Object.getPrototypeOf(child) === parent); // true

• Object.setPrototypeOf(obj, proto) - Sets the prototype of an object

  const newProto = { sayHi: () => "Hi!" };
  Object.setPrototypeOf(child, newProto);
  console.log(child.sayHi()); // "Hi!"

• Object.hasOwn(obj, prop) - Checks if an object has a property (ES2022+)

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

• Object.hasOwnProperty(prop) - Checks if an object has a property (older method)

  console.log(obj.hasOwnProperty("age")); // true

• Object.getOwnPropertyNames(obj) - Returns an array of all property names

  console.log(Object.getOwnPropertyNames(obj)); // ["name", "age"]

• Object.getOwnPropertyDescriptors(obj) - Returns property descriptors

  console.log(Object.getOwnPropertyDescriptors(obj));

• Object.defineProperty(obj, key, descriptor) - Defines a new property

  Object.defineProperty(obj, "gender", { value: "male", writable: false });
  console.log(obj.gender); // "male"

• Object.defineProperties(obj, props) - Defines multiple properties

  Object.defineProperties(obj, {
      country: { value: "USA", writable: true },
      hobby: { value: "Reading", writable: false }
  });
  console.log(obj.country, obj.hobby); // "USA" "Reading"

• Object.is(value1, value2) - Compares two values (like === but handles NaN correctly)

  console.log(Object.is(NaN, NaN)); // true