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JavaScript Quiz – can array have the size method like a set

JavaScript Quiz – can array have the size method like a set

Array Size Method

javascript Array size method is not a method that exists in an array because the array has a length property that provides the length of the array. But in javascript, we can create a new method that attaches to the array prototype.

So, new method can be created and attach to array. Let’s have an syntax of array prototype

Array.prototype.clear = function(){
  // statement

For more detail about the javascript array prototype click here.

JavaScript Question

In this javascript quiz, find out can array has the size method like a set because the array has a length property, not a size method.

First, we add a prototype method to the array with a method name size in which we return the length of the array.

Array.prototype.size = function(){
   return this.length;

In the next step, we create an variable with name array and assign an javascript array which contain only number.

let array = [1, 2, 3];

Now we use the size method and print it’s value using console log.


Any idea what should be the output of above code statement.

JavaScript Quiz Test

Here is the full javascript code snippet for you to solve.

Array.prototype.size = function(){
   return this.length;

let array = [1, 2, 3]
console.log(array.size());  // output => 🧐 ?

// Made with ❤️, by @jsstartup

Answer – 3

Click To Run Code


Now, you know the answer is “3“. But why because array doesn’t have a size method. Let me explain.

So, first, we add javascript size method in array as prototype which means it can directly use that method.

And inside that, we can see that it return length with this keyword. Because this holds the array.

As a result, the size() method works because we can create a custom array prototype method.

At last, That’s why we get an answer “3“.

Let me know in the comment section, what you think about it.

I hope you understand the concept and logic behind it.

But wait, i have something more for you –

Check out our other javascript quiz – 

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