Combine arr1 and arr2

JavaScript
1

The following code works fine as arr2 is empty, and arr2 got the contents of arr1, but I’m really confused that if arr2 is not empty, like arr2 = [‘JUNE’, ‘JULY’], anybody can tell me how I can put arr1 and arr2 together? I hope I’ve made me clear, thanks.

Your code so far


const arr1 = ['JAN', 'FEB', 'MAR', 'APR', 'MAY'];
let arr2;

arr2 = [...arr1]; 

console.log(arr2);

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2

This line here says "ignore the contents of arr2 and replace it with a shallow copy of arr1"

1 Like
3

As it stands, your code is replacing the value in arr2. But if you modified the [...arr1] to include arr2 somehow… :thinking:

1 Like
4

There are a couple of ways to join arrays in JS. Here are 2 common ways:

  1. let arr3 = arr2.concat(arr1)
    // does not modify arr1 and arr2

  2. arr2 = [...arr2, ...arr1]
    // modifies arr2

  3. arr3 = [...arr1, ...arr2]
    // does not modify arr1 and arr2

2 Likes
5

Thanks, it works :grinning: :grinning: :grinning:

1 Like
6

technique1: arr1.concat(arr2)
technique2: const arr2 = [a, b, c, …arr1]

1 Like
7

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