Advanced Object Methods

JavaScript objects are an essential data type for effectively structuring and managing data.

Here, we'll look at fundamental methods for handling the keys, values, and properties of objects.

This method returns an array of all the keys of an object.

Copy
const person = {
  name: 'Emma',
  age: 28,
  city: 'New York',
};

const keys = Object.keys(person);
console.log(keys); // ["name", "age", "city"]

Returns an array of all values of an object.

Copy
const person = {
  name: 'Emma',
  age: 28,
  city: 'New York',
};

const values = Object.values(person);
console.log(values); // ["Emma", 28, "New York"]

Returns all key-value pairs of an object as a two-dimensional array.

Copy
const person = {
  name: 'Emma',
  age: 28,
  city: 'New York',
};

const entries = Object.entries(person);
console.log(entries);
// [["name", "Emma"], ["age", 28], ["city", "New York"]]

When you want to perform operations on each property of an object, Object.keys or Object.entries can be handy.

Example: Print all values of an object

Copy
const person = {
  name: 'Emma',
  age: 28,
  city: 'New York',
};

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

// or

for (let [key, value] of Object.entries(person)) {
  console.log(value);
}

• Object.assign(target, ...sources): Copies all enumerable properties from one or more source objects to a target object. Returns the target object.

  Merging objects

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  let obj1 = { a: 1, b: 2 };
  let obj2 = { b: 3, c: 4 };
  
  let combined = Object.assign({}, obj1, obj2);
  console.log(combined); // { a: 1, b: 3, c: 4 }

• Object.freeze(obj): Freezes an object so that its properties cannot be added, removed, or modified.

  Freezing an object

  Copy
  Object.freeze(person);
  person.major = 'Software'; // Error! Cannot add properties to a frozen object