var YAHOO = window.YAHOO || {};YAHOO.namespace = function(ns) {
if (!ns || !ns.length) { return null;
} var levels = ns.split("."); var nsobj = YAHOO; // YAHOO
is implied, so it is ignored if it is included for (var i=(levels[0] == "YAHOO") ? 1 : 0;
i<levels.length; ++i) {
nsobj[levels[i]] = nsobj[levels[i]] || {};
nsobj = nsobj[levels[i]];
} return nsobj;
};YAHOO.extend = function(subclass,
superclass) { var f = function() {};
f.prototype = superclass.prototype;
subclass.prototype = new f();
subclass.prototype.constructor = subclass;
subclass.superclass = superclass.prototype; if (superclass.prototype.constructor == Object.prototype.constructor) {
superclass.prototype.constructor = superclass;
}};YAHOO.namespace("util");YAHOO.namespace("widget");YAHOO.namespace("example");原文：http://www.cnblogs.com/rongfengliang/p/3599453.html