make_flat.js

/**	make_flat(Array)
 *	Simple method for flattening a multidimensional array
 *	@example make_flat([[1,2,[3]],4]) == [1, 2, 3, 4]
**/
function make_flat(arr) {
	//	simply make use of `reduce` method to to reduce each element to a single val
	return arr.reduce(function(a, b) {
			//	if val is array, rerun thru, else, move on
			return a.concat( Array.isArray(b) ? make_flat(b) : b );
		},
  		[]
	);
}

/*	arbitrarily, for simplicity, could be written using a simple arrow function as:
	function make_flat(arr) {
		return arr.reduce( (acc, val) => acc.concat( Array.isArray(val) ? make_flat(val) : val ), [] );
	}
*/

/**	See Simple Test @
 *		https://jsperf.com/flatten-js-array/1
**/