写自已的js类库需要的核心代码

(function(win) { 
var toString = Object.prototype.toString; 
var hasOwn = Object.prototype.hasOwnProperty; 
var class2type = {}; 
class2type["[object Boolean]"] = "boolean"; 
class2type["[object Number]"] = "number"; 
class2type["[object String]"] = "string"; 
class2type["[object Function]"] = "function"; 
class2type["[object Array]"] = "array"; 
class2type["[object Date]"] = "date"; 
class2type["[object RegExp]"] = "regexp"; 
class2type["[object Object]"] = "object"; 
win.type = function(obj) { 
return obj == null ? String(obj) : class2type[toString.call(obj)] || "object"; 
}; 
win.isBoolean = function(obj) { 
return type(obj) === "boolean"; 
}; 
win.isNumber = function(obj) { 
return type(obj) === "number"; 
}; 
win.isString = function(obj) { 
return type(obj) === "string"; 
}; 
win.isDate = function(obj) { 
return type(obj) === "date"; 
}; 
win.isRegExp = function(obj) { 
return type(obj) === "regexp"; 
}; 
win.isObject = function(obj) { 
return type(obj) === 'object'; 
}; 
win.isFunction = function(obj) { 
return type(obj) === "function"; 
}; 
win.isArray = function(obj) { 
return type(obj) === "array"; 
}; 
win.isWindow = function(obj) { 
return obj 
&& typeof obj === "object" 
&& "setInterval" in obj; 
}; 
win.isNumeric = function(obj) { 
return !isNaN(parseFloat(obj)) && isFinite(obj); 
}; 
win.isPlainObject = function(obj) { 
if (!obj 
|| type(obj) !== "object" 
|| obj.nodeType 
|| isWindow(obj)) { 
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); 
}; 
win.isEmptyObject = function(obj) { 
for ( var name in obj) { 
return false; 
} 
return true; 
}; 
win.isPrimitive = function(obj){ 
var type = typeof obj; 
return type === 'string' || type === 'number' || type === 'boolean'; 
}; 
//HTMLElement 
win.isElement = function(obj){ 
return obj ? obj.nodeType === 1 : false; 
}; 
//TextNode 
win.isTextNode = function(obj){ 
return obj ? obj.nodeName === "#text" : false; 
}; 
win.isIterable = function(obj){ 
return (obj && typeof obj !== 'string') ? obj.length !== undefined : false; 
}; 
win.isDefined = function(obj){ 
return typeof obj !== 'undefined'; 
}; 
win.error = function(msg) { 
throw new Error(msg); 
}; 
win.now = function() { 
return (new Date()).getTime(); 
}; 
win.print = function(value) { 
document.write(value); 
}; 
win.println = function(value) { 
print(value); 
document.write("
"); 
}; 
win.each = function(object, callback, args) { 
var name, i = 0, 
length = object.length, 
isObj = (length === undefined || isFunction(object)); 
if (args) { 
if (isObj) { 
for (name in object) { 
if (callback.apply(object[name], args) === false) { 
break; 
} 
} 
} else { 
for (; i 

如果我们不用extend方法，可以象下面的方式写自己的组件：

(function(win){ 
win.StringBuffer = function(){ 
this.datas = []; 
} 
var proto = StringBuffer.prototype; 
proto.append = function(value){ 
this.datas.push(value); 
}, 
proto.toString = function(){ 
return this.datas.join(""); 
} 
})(window);

如果使用extend方法，可以象下面这样写组件：

(function(win){ 
win.extend(win,{ 
StringBuilder : function(){ 
this.datas = []; 
} 
}); 
win.extend(StringBuilder.prototype, { 
append : function(value){ 
this.datas.push(value); 
}, 
toString : function(){ 
return this.datas.join(""); 
} 
}); 
})(window);

两种方法的效果一样，但是extend方法还可以做更多事件，比如插件式开发，跟第二种方式很象。
当然，如果你本来就想写jQuery插件，那就直接用jQuery的extend就可以啦。