new Keyword

In this lesson, you'll learn about the keyword in JavaScript, which is crucial for creating objects and understanding how JavaScript handles object-oriented programming.

Introduction

The keyword in JavaScript is used to create a new object. At its core, the keyword performs a simple yet powerful function: it creates a new object. Let's explore this with some code examples.

Creating an Object with new

When you use the keyword, you create an empty object. Here's how you can create an object using the keyword:

const person = new Object();

This line of code creates an empty object called . It's equivalent to writing . You can add properties to this object just like any other object:

person.lastname = "John";
console.log(person.lastname); // prints "John"

You can also check the type of the object:

console.log(typeof person); // prints "object"

Object Methods & Object() Constructor

The function is a built-in constructor in JavaScript that allows you to create objects. You can also define your own constructor functions to create objects of a specific type.

Creating Custom Constructors

Here's how you can create a custom constructor function:

function Person(name, age, profession) {
  this.name = name;
  this.age = age;
  this.profession = profession;
}

const john = new Person("John", 23, "Teacher");
console.log(john.name); // prints "John"

In this example, we created a constructor function and used the keyword to create an instance of .

NEW & THIS (Keywords)

The keyword binds to the new object being created. In the constructor function, refers to the new object.

function Person(name, age, profession) {
  this.name = name;
  this.age = age;
  this.profession = profession;
}

Built-in Constructors and Methods

JavaScript provides several built-in constructors like Date, Array, Number, etc. When you use the new keyword with these constructors, you create objects with built-in methods.

const myDate = new Date('August 11, 2025');
console.log(myDate.getFullYear()); // prints 2025

These constructors provide methods that you can use on the objects they create. For example, arrays have methods like pop, push, slice, and splice.

Literal Syntax vs. new Keyword

JavaScript also provides literal syntax for creating objects and arrays, which is a shorthand for using the new keyword.

const names = ['wes', 'kait'];
console.log(typeof names); // prints "object"
console.log(names instanceof Array); // prints true

The literal syntax is a more concise way to create objects and arrays, but under the hood, they are still objects with methods.

Understanding the new keyword and how it interacts with constructors and the this keyword is essential for mastering object-oriented programming in JavaScript.

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