How to insert elements in an array at a particular index in case the elements are themselves in another array?

Question

Suppose, I have two arrays :

A = [1, 2, 3, 4]

B = [10, 20, 30].

and I want to insert B's elements in array A starting from index 1. So, my final array would look like

[1, 10, 20, 30, 2, 3, 4]

I tried to do it with splice. But the splice function requires you to provide list of elements, not an array.

Is there any way to achieve it?

CertainPerformance · Accepted Answer · 2019-03-10 20:00:47Z

2

You can just spread B into the argument list of splice:

const A = [1, 2, 3, 4]
const B = [10, 20, 30]
A.splice(1, 0, ...B); // equivalent to `.splice(1, 0, 10, 20 30)`
console.log(A);

answered Mar 10, 2019 at 20:00

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Comments

Shidersz · Accepted Answer · 2019-03-10 20:18:13Z

1

You can also do this with Array.slice() and spread syntax. Note that Array.splice() mutates the array:

The splice() method changes the contents of an array by removing or replacing existing elements and/or adding new elements in place.

But, if you are looking to change array A then splice() is fine as shown on the other answers.

const A = [1, 2, 3, 4];
const B = [10, 20, 30];
const C = [...A.slice(0,1), ...B, ...A.slice(1)];
console.log(C);

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answered Mar 10, 2019 at 20:12

Shidersz

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Pranav C Balan · Accepted Answer · 2019-03-10 20:09:30Z

0

You can use splice with Function#apply method or ES6 spread syntax.

var A = [1, 2, 3, 4],

B = [10, 20, 30];

[].splice.apply(A,[1,0].concat(B));

console.log(A)

var A = [1, 2, 3, 4],

  B = [10, 20, 30];

A.splice(1, 0, ...B)

console.log(A)

answered Mar 10, 2019 at 20:02

Pranav C Balan

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