Object.extend() implement from jQuery

jQuery.extend.js

  {
    //Object.extend comes from jQuery
  	extend: function () {
  		var options, name, src, copy, copyIsArray, clone, target = arguments[0] || {},
  			i = 1,
  			length = arguments.length,
  			deep = false,
  			toString = Object.prototype.toString,
  			hasOwn = Object.prototype.hasOwnProperty,
  			push = Array.prototype.push,
  			slice = Array.prototype.slice,
  			trim = String.prototype.trim,
  			indexOf = Array.prototype.indexOf,
  			class2type = {
  				"[object Boolean]": "boolean",
  				"[object Number]": "number",
  				"[object String]": "string",
  				"[object Function]": "function",
  				"[object Array]": "array",
  				"[object Date]": "date",
  				"[object RegExp]": "regexp",
  				"[object Object]": "object"
  			},
  			jQuery = {
  				isFunction: function (obj) {
  					return jQuery.type(obj) === "function";
  				},
  				isArray: Array.isArray || function (obj) {
  					return jQuery.type(obj) === "array";
  				},
  				isWindow: function (obj) {
  					return obj !== null && obj === obj.window;
  				},
  				isNumeric: function (obj) {
  					return !isNaN(parseFloat(obj)) && isFinite(obj);
  				},
  				type: function (obj) {
  					return obj === null ? String(obj) : class2type[toString.call(obj)] || "object";
  				},
  				isPlainObject: function (obj) {
  					if (!obj || jQuery.type(obj) !== "object" || obj.nodeType) {
  						return false;
  					}
  					try {
  						if (obj.constructor && !hasOwn.call(obj, "constructor") && !hasOwn.call(obj.constructor.prototype, "isPrototypeOf")) {
  							return false;
  						}
  					} catch (e) {
  						return false;
  					}
  					var key;
  					for (key in obj) {}
  					return key === undefined || hasOwn.call(obj, key);
  				}
  			};
  		if (typeof target === "boolean") {
  			deep = target;
  			target = arguments[1] || {};
  			i = 2;
  		}
  		if (typeof target !== "object" && !jQuery.isFunction(target)) {
  			target = {};
  		}
  		if (length === i) {
  			target = this;
  			--i;
  		}
  		for (i; i < length; i++) {
  			if ((options = arguments[i]) !== null) {
  				for (name in options) {
  					src = target[name];
  					copy = options[name];
  					if (target === copy) {
  						continue;
  					}
  					if (deep && copy && (jQuery.isPlainObject(copy) || (copyIsArray = jQuery.isArray(copy)))) {
  						if (copyIsArray) {
  							copyIsArray = false;
  							clone = src && jQuery.isArray(src) ? src : [];
  						} else {
  							clone = src && jQuery.isPlainObject(src) ? src : {};
  						}
  						// WARNING: RECURSION
  						target[name] = extend(deep, clone, copy);
  					} else if (copy !== undefined) {
  						target[name] = copy;
  					}
  				}
  			}
  		}
  		return target;
  	}
  }