Objects

Objects store key-value pairs of data and can define behaviour via functions.

Creation

Empty Object

let person = {};

Object With values

let person = { name: 'Emily', age: 26 };

Accessing Values

Values are accessed through keys.

let person = { name: 'Emily', age: 26 }; console.log(person.name);

Output:

Emily

Setting Keys

Let's add key-value pair to object and then modify it:

let car = {}; // Add key-value to object: car.hp = 90; console.log(car.hp); // Edit value car.hp = 100; console.log(car.hp);

Output:

90 100

Function

An object may contain function in which this points to the object itself.

Let's look at the following example:

let person = { name: "Jo", city: "Chicago", present: function() { console.log("Hello, I'm " + this.name + " from " + this.city ); } }; person.present();

In order to access object's property (name and city) the keyword this is used.

Iterating

In order to loop through object's keys and values Object.entries can be used.

let drinks = { 'Orange Juice': 2.45, 'Water': 0.80, 'Coke': 1.45 }; for (const [key, value] of Object.entries(drinks)) { console.log(key + ': ' + value); }

Output:

Orange Juice: 2.45 Water: 0.8 Coke: 1.45

Notice: Object.entries cannot be used in Internet Explorer.