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

The spread operator allows an expression to be expanded in places where multiple arguments (for function calls) or multiple elements (for array literals) are expected.

a2 = [21,22];
a1 = [1,2,...a2,3,4,5];//...a2 is use of spread operator
console.log(a1);