Javascript flatten

flatten.js

// Flatten an array with possible nested array into a single array
function flatten(arr) {
	if (!Array.isArray(arr))
		// Do nothing if we're not an array
		return(arr);
	var ret = [];
	var i, j;
	for (i = 0; i < arr.length; i++) {
		// Flatten each individual element
		var aux = flatten(arr[i]);
		if (Array.isArray(aux))
			// If we're an array, push each element into our return array
			for (j = 0; j < aux.length; j++)
				ret.push(aux[j]);
		else
			// If we're not an array, just push the element to the return array
			ret.push(aux);
	}

	return(ret);
}

/* Some testing cases:
console.log(flatten([[1, 2, [3]], 4]));	// Expect [1, 2, 3, 4]
console.log(flatten([[[[[ 5 ]]]]]));	// Expect [5]
console.log(flatten([1, 2, 3, 4]));		// Expect [1, 2, 3, 4]
console.log(flatten([[1,2],[3,4]]));	// Expect [1, 2, 3, 4]
console.log(flatten([[1,2],[3,4], [[5,6],[7,8]]])); // Expect [1, 2, 3, 4, 5, 6, 7, 8]
*/