Flatten an array of arbitrarily nested arrays of integers into a flat array of integers

flatten.js

//Set the array of arbitrarily nested arrays to startArray
//The flattened array is stored in endArray after flatten(startArray) is executed

var startArray = [[1,2,[3]],4];
var endArray = new Array();

flatten(startArray);

console.log('original:      ' + startArray);
console.log('flattened:     ' + endArray);

function flatten(input, output)
{
	for (var i = 0; i < input.length; i++)
	{
		if (typeof(input[i]) === "object")
		{
			flatten(input[i]);
		}
		else
		{
			endArray.push(input[i]);
		}
	}
}