FlattenArray.js

/**
 * Flatten an Array of Integers
 * 
 * @param  {Array} integers_array - Array of Numbers
 * @return {Array}                - Array of Numbers , flattened
 * 
 */
function flatten(integers_array) {

	all_results = [];

	if (integers_array && integers_array instanceof Array && integers_array.length > 0) {
		integers_array.forEach(function(value) {
			if (typeof value === 'number') {
				all_results.push(value);
			} else if (value instanceof Array && value.length > 0) {
				all_results = all_results.concat(flatten(value));
			}
		});
	}
	return all_results;
}
/**
 * This is a utility function to pring the array under test.
 */

function print_array_as_string(integers_array) {

	all_results = "[";

	if (integers_array && integers_array instanceof Array && integers_array.length > 0) {
		integers_array.forEach(function(value) {
			if (!(value instanceof Array)) {
				all_results += ((all_results.length > 1 || value === undefined) ? "," : "") + value;
			} else if (value instanceof Array) {
				all_results += ((all_results.length > 1) ? "," : "") + "[" + flatten(value) + "] ";
			}
		});
	}
	return all_results + "]";
}
/**
 *  This is a method to test the array passed in by printing both the forms.
 */

function test_flatten_with(test_arr) {

	console.log(print_array_as_string(test_arr) + " flattened array :  ", print_array_as_string(flatten(test_arr)));
}

/**
 *
 *  This is a method used to run all the tests in this function.
 */
function test_suite_flatten() {


	test_flatten_with([, , , 1, 2, 3, [4, 5]]);

	test_flatten_with([[1, 2], 3, [4, 5]]);

	test_flatten_with([[1, 2],[[3]],[4, 5]]);

	test_flatten_with([[],[[3]],[5]]);

	test_flatten_with([[1],['a']]);

	test_flatten_with([[1],[2, 3, 4]]);

	test_flatten_with([[1],[[2, [[3]]],[4]]]);

    test_flatten_with([[1],[[2, [[3]]],[undefined]]]);

    test_flatten_with(undefined);

}

test_suite_flatten();