How to replace elements in array with elements of another array

Question

I want to replace elements in some array from 0 element, with elements of another array with variable length. Like:

var arr = new Array(10), anotherArr = [1, 2, 3], result; result = anotherArr.concat(arr); result.splice(10, anotherArr.length); 

Is there some better way?

Answer 1

You can use the splice method to replace part of an array with items from another array, but you have to call it in a special way as it expects the items as parameters, not the array.

The splice method expects parameters like (0, anotherArr.Length, 1, 2, 3), so you need to create an array with the parameters and use the apply method to call the splice method with the parameters:

Array.prototype.splice.apply(arr, [0, anotherArr.length].concat(anotherArr)); 

Example:

var arr = [ 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j']; var anotherArr = [ 1, 2, 3 ];  Array.prototype.splice.apply(arr, [0, anotherArr.length].concat(anotherArr));  console.log(arr); 

Output:

[ 1, 2, 3, 'd', 'e', 'f', 'g', 'h', 'i', 'j'] 

Demo: http://jsfiddle.net/Guffa/bB7Ey/