Javascript - insert an array inside another array

Question

What is the more efficient way to insert an array inside another array.

a1 = [1,2,3,4,5];
a2 = [21,22];

newArray - a1.insertAt(2,a2) -> [1,2, 21,22, 3,4         


        

Answer 1

You can now do this if using ES2015 or later:

var a1 = [1,2,3,4,5];
var a2 = [21,22];
a1.splice(2, 0, ...a2);
console.log(a1) // => [1,2,21,22,3,4,5]

Refer to this for documenation on the spread (...) operator https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Spread_operator