JS prototype method that flattens an array that contains nested arrays

array-flattener.js

/**
 * Flattens the array that contains nested arrays, optionally removing null or undefined elements.
 * @example 
 * // returns [1, 2, 3, null, undefined, 4]
 * [[1,2,[3,null],undefined],4].flatten()
 * @example 
 * // returns [1, 2, 3, 4] 
 * [[1,2,[3,null],undefined],4].flatten(true)
 * @param removeBlanks {boolean} If evaluates to true, strips any null or undefined array elements.
 * @returns {Array} Flattened array of elements of the original array and any of its nested arrays.
 */     
Array.prototype.flatten = function(removeBlanks) {
    removeBlanks = removeBlanks || false;    
    
    var result = [];

    function _flatten(arr) {
        for (var i = 0; i < arr.length; i++) {
            var el = arr[i];
            if (el != null && typeof el === "object" && typeof el.length !== "undefined") {
                _flatten(el);
            }
            else if (!removeBlanks || (typeof el !== "undefined" && el !== null)) {
                result.push(el);
            }
        }
    }

    _flatten(this);

    return result;
};