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JavaScript Quiz – can array from method be like a map method

JavaScript Quiz – can array from method be like a map method

Array from method –

In javascript array from method (Array.from()) is used to create a new array from an array-like or iterable object.

Array from method create a shallow copied array.

It’s syntax look like –

Array.from(object, mapFunction, thisValue)

For more information about javascript array.from() click here.

JavaScript Question

In this javascript quiz, find out that the javascript array from the method can be like a map method to modify the value in an array.

First, we create a variable array using the let keyword and assign a javascript array to it which contains only a number element.

let array = [1, 3, 5];

In the next step, we use an Array.from() and pass an array variable to it and also pass a function which multiplies each element with 3 like an array map method.

And assign the array returned from Array.from() to new variable newArray which is created with let.

let newArray = Array.from(array, x => x*3);

Now, we change index 1 of the array variable to 6. And then check the value of index 1 of the newArray variable.

array[1] = 6;


So, Any guess what will the output of console log ?

Answer – 9

Click To Run Code


Now, you know the answer is 9. But you want to know why, it should be 6 or does it work like a map in array from method. Let me explain.

So, it’s true that Array.from() can be work like an Array.map() as it also contains a map function in it that runs for every element in the array.

As if you remember that Array.from() creates a new array and it’s a shallow copy. This means any change in the array variable will not reflect on the newArray.

Array.from() with mapFunction –

And we use a mapFunction in array from method to change the element value by multiply 3. So it should be like.

let newArray = [3, 9, 15];

At last, That’s why we get an answer “9“.

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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