Flatten an array

/**
 * Flatten an array
 * E.g [[1,2,[3]],4] -> [1,2,3,4] 
 * 
 * @Contributor Rahul Shetty <rahulshetty@helpshift.com>
 * @created Wed Feb 15 12:40:37 2017
 */
 
 function flattenNestedArray(arr) {
    var result = [];
    for(var i = 0; i < arr.length; i++) {
        if(Array.isArray(arr[i])) {
            result = result.concat(flattenNestedArray(arr[i]));
        } else {
            result.push(arr[i]);
        }
    }
    return result;
}

var flattenedArray = flattenNestedArray([[1,2,[3]],4]);
console.log (flattenedArray);