Implementation of array_merge for JavaScript

array_merge.js

/**
 * @fileoverview array_merge and supporting functions.
 * Designed to mimic PHP's array_merge function, however
 * this function also takes into account that objects are
 * used in place of associative arrays in JavaScript.
 * @author Andrew Noyes noyesa@gmail.com
 */
 
(function () {
	/**
	 * Returns the class name of object.
	 * @param object {Object}
	 * @returns Class name of object
	 * @type String
	 */
	 var getClass = function (object) {
	   return Object.prototype.toString.call(object).slice(8, -1);
	 };
  
   /**
    * Returns true of obj is a collection.
    * @param obj {Object}
    * @returns True if object is a collection
    * @type {bool}
    */
	var isValidCollection = function (obj) {
		try {
			return (
				typeof obj !== "undefined" &&  // Element exists
				getClass(obj) !== "String" &&  // weed out strings for length check
				typeof obj.length !== "undefined" &&  // Is an indexed element
				!obj.tagName &&  // Element is not an HTML node
				!obj.alert &&  // Is not window
				typeof obj[0] !== "undefined"  // Has at least one element
			);
		} catch (e) {
			return false;
		}
	};
  
	/**
	 * Merges an array with an array-like object or
	 * two objects.
	 * @param arr1 {Array|Object} Array that arr2 will be merged into
	 * @param arr2 {Array|NodeList|Object} Array-like object or Object to merge into arr1
	 * @returns Merged array
	 * @type {Array|Object}
	 */
	window.array_merge = function (arr1, arr2) {
		// Variable declarations
		var arr1Class, arr2Class, i, il;

		// Save class names for arguments
		arr1Class = getClass(arr1);
		arr2Class = getClass(arr2);

		if (arr1Class === "Array" && isValidCollection(arr2)) {  // Array-like merge
			if (arr2Class === "Array") {
				arr1 = arr1.concat(arr2);
			} else {  // Collections like NodeList lack concat method
				for (i = 0, il = arr2.length; i < il; i++) {
					arr1.push(arr2[i]);
				}
			}
		} else if (arr1Class === "Object" && arr1Class === arr2Class) {  // Object merge
			for (i in arr2) {
				if (i in arr1) {
					if (getClass(arr1[i]) === getClass(arr2[i])) {  // If properties are same type
						if (typeof arr1[i] === "object") {  // And both are objects
							arr1[i] = array_merge(arr1[i], arr2[i]);  // Merge them
						} else {
							arr1[i] = arr2[i];  // Otherwise, replace current
						}
					}
				} else {
					arr1[i] = arr2[i];  // Add new property to arr1
				}
			}
		}
		return arr1;
	};
  
})();
 
var a1 = {'aa':100, 'bb':2, 'cc':[6,7], 'dd':[12,13], 'ee':{'15':15,'16':16}};
var b1 = {'xx':101, 'bb':5, 'cc':8, 'dd':[14,15], 'ee':{'17':17,'18':18}};
var c = array_merge(a1, b1);
console.log(c);
// Output: {’aa’:100, ‘bb’: 5, ‘cc’:[6,7], ‘dd’:[12,13,14,15], ‘ee’:{’15′:15,’16′:16,’17′:17,’18′:18}, ‘xx’:101}