Introduction

JavaScript object is a non-primitive data type that allows you to store multiple collections of key/value pairs and more complex entities.

Object Declaration

Here, an object Object name is defined. Each member of an object is a key: value pair separated by commas and enclosed in curly braces {}.

Example:

const user = {
    firstName: 'John',
    lastName: 'Due',
};

Accessing Elements

To get a Complete Object

const user = {
    firstName: 'John',
    lastName: 'Due',
};

console.log(user)

Output:

{
    firstName: 'John',
    lastName: 'Due',
}

To get an element from an Object

const user = {
    firstName: 'John',
    lastName: 'Due',
};

console.log(user.firstName)  // dot notation
        // OR
console.log(user['firstName'])  // bracket notation

Output:

'John'

Here, it calls the objects key to get its value.

To get an element from an Object of another Object

const user = {
    name:{
        firstName: 'John',
        lastName: 'Due',
    }
};

console.log(user.name.firstName)

Output:

'John'

Methods

The JavaScript method is an object property that has a function value.

User Defined Methods

Declaring Methods

const user = {
    name: function(){
        return "John"
    }
};

Accessing Methods

const user = {
    name: function(){
        return "John"
    }
};

console.log(user.name())

Output:

John

Built-In Methods

Object.create()

The Object.create() method is used to create a new object and link it to the prototype of an existing object.

Object.create(proto)

const user = {
    firstName: 'John',
    lastName: 'Due',
};
const person1 = Object.create(user);
console.log(person1.firstName)

Output:

John

Object.values()

Object.values() creates an array containing the values of an object.

Object.values(obj)

const user = {
    firstName: 'John',
    lastName: 'Due',
};
const name = Object.values(user);
console.log(name)

Output:

[ 'John', 'Due' ]

Object.keys()

Object.keys() creates an array containing the keys of an object.

Object.keys(obj)

const user = {
    firstName: 'John',
    lastName: 'Due',
};
const name = Object.keys(user);
console.log(name)

Output:

[ 'firstName', 'lastName' ]

Object.entries()

Object.entries() creates a nested array of the key/value pairs of an object.

Object.entries(obj)

const user = {
    firstName: 'John',
    lastName: 'Due',
};
const name = Object.entries(user);
console.log(name)

Output:

[ 
    [ 'firstName', 'John' ], 
    [ 'lastName', 'Due' ] 
]

Object.fromEntries()

Object.fromEntries() creates an object array a nested array.

Object.fromEntries(obj)

const user = [ [ 'firstName', 'John' ], [ 'lastName', 'Due' ] ]
const name = Object.fromEntries(user);

console.log(name);

Output:

{ 
    firstName: 'John', 
    lastName: 'Due' 
}

Object.freeze()

Object.freeze() prevents modification to properties and values of an object.

Object.freeze(obj)

const user = {
    firstName: 'John',
    lastName: 'Due',
};
const name = Object.freeze(user);
name.firstName= 'Mario'
name.middleName= 'Bros'
console.log(name)

Output:

{ firstName: 'John', lastName: 'Due' }

Object.seal()

Object.seal() prevents new properties from being added to an object, but allows the modification of existing properties.

Object.seal(obj)

const user = {
    firstName: 'John',
    lastName: 'Due',
};
const name = Object.seal(user);
name.firstName= 'Mario'
name.middleName= 'Bros'
console.log(name)

Output:

{ firstName: 'Mario', lastName: 'Due' }

Object.assign()

Object.assign() is used to copy values from one or objects to another object.

Object.assign(destination_objects, ...source_objects)

const name1 = {
    firstName: 'John',
};
const name2 = {
    lastName: 'Due',
};
Object.assign(name2, name1); // Also returns value of name2
console.log(name2)

Output:

{ lastName: 'Due', firstName: 'John' }

Object.is()

The Object.is() method determines whether two values are the same or not.

Object.is(value1, value2)

const user = { firstName: 'John', lastName: 'Due' }
const obj = Object.is(user.firstName, 'John');

console.log(obj);

Output:

true