Flatten array algorithm in javascript

flattenArray.js

/**
	Convert nested array to flat array
*/

function flattenArray(arr) {
	/**
		Create en empty array. In this array we will push elements from nested array passed 
		as a parameter.
	*/
	var flatArray = [];

	/**
		Iterate through array in classic 'for' loop. 
	*/

	for (var i = 0; i < arr.length; i++) {
		/**
			check if the current element of array is an instanse of 'Array' type.
			If so, we call this function again (recursion) and pass as a parameter
			array which was at index 'i' if original passed array...
		*/
		if (arr[i] instanceof Array) {

			/**
				Create constant that holds result of nested array. In our case nested array is
				value at index 'i' in passed 'arr' array
			*/
			const recursionResult = flattenArray(arr[i]);

			/**
				iterate through array (nested) of element 'i' and push elements of this array to 
				array created earlear ('flatArray')
			*/
			for (var j = 0; j < recursionResult.length; j++) {
				flatArray.push(recursionResult[j]);
			}
		} else {
			/**
				Adds element of passed array to 'flatArray'
			*/
			flatArray.push(arr[i]);
		}
	}

	/**
		returns flat array
	*/

	return flatArray;
}


/**
	Usage
*/


const nestedArray = [1, 2, 3, [4, 5], [6, [5, 0]], 44, ["some string", [[10, 11], [12, 13]], 4.9]];

console.log(flattenArray(nestedArray));