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

If you want to insert another array into an array without creating a new one, the easiest way is to use either push or unshift with apply

Eg:

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

// Insert a1 at beginning of a2
a2.unshift.apply(a2,a1);
// Insert a1 at end of a2
a2.push.apply(a2,a1);

This works because both push and unshift take a variable number of arguments. A bonus, you can easily choose which end to attach the array from!