Additional menu

CodingWithDrew

A Web and App Development Portfolio

You are here: Home / Basics & Fundamentals / Understanding `new` In Javascript

Understanding `new` In Javascript

//new

Javascript has some interesting tools such as new or this built in that you probably have seen used but never new how to use it outside of a tutorial or project you followed from someone else. I know I haven't really covered new just yet either and hope you find this to be a valuable resource!

What is the new keyword? Let's first examine it.

// new Example

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

Testing it out

If you open the console, you will see tons of methods on the console.log(myDate). Where did the myDate.getFullYear come from?

When you create a any object, number, or string, it's extended off the constructor - If you look at all the types we have - you will see they are technically an object. In your console you can type Array and the result will be a function Array(). These functions, when we add new to the front of that, it returns an object.

const myNumber = new Number (100); If we type in myNumber to the console - you will see a bunch of methods that exist on it. This is what we mean when we say everything in Javascript is an object.

Let's go back to the date example above.

Testing it out a step further

We have an instance of Date and if we type typeof myDate in the console, you will see it's an object. Similarly, if we type myDate instanceof Date we will see the result is true.

Literals

We don't need to type in new when creating an array.
For Example: const names = ['drew', 'audrey']; we don't need to put new in front of it. Why is that? If we use the console for type of names we see it's an object. We see that it's an Object (it's not an Array, which is a special kind of object). But if we say names instanceof Array we see it's true. Why is that? That's because this is what we consider literal syntax.

const names = ['drew', 'audrey']; === const names = new Array('drew', audrey');. Since the left side of this example is "Array Literal, we don't have to use the "new" keyword.

Let's make a pizza!

function Pizza() {
    console.log('Making a pizza');
}
const pepperoniPizza = Pizza();
console.log(pepperoniPizza);

We can run this and you can see we get undefined. That makes sense because the function didn't return anything. What happens if we just add new to that?

function Pizza() {
    console.log('Making a pizza');
}
const pepperoniPizza = new Pizza();
console.log(pepperoniPizza);

You get a new empty Pizza{} (pizza object)! It creates a new instance object of that function instead of what ever has been returned from that function.

My Final Thoughts and Ask

By using the new keyword in Javascript, that creates a new object that is an instance of what ever function you have made it from.

If you found this article helpful, share/retweet it and follow me on twitter @codingwithdrewk!

There is a lot more to learn in Javascript, the new keyword is a tricky one but I hope that this article helps to clear it up!