Flatten deeply nested Array of Integers

flattenArrays.js

/*
@input: Input array to be flattened
@result: Empty Array

@return: 
   invalid input: Empty Array
   valid input (an Array): Flattened Array
*/

function flatten(input, result) {
	
	if (Number.isInteger(input)) result.push(input);

	if (Array.isArray(input)) {
		input.forEach(function(element) {
			flatten(element, result)

		})
	}

	return result;
}