<script type="text/javascript">var f = function() {alert('原有函数');}var _f = f;f = function() {alert('执行前置包装函数');_f();alert('执行后置包装函数');}f();
</script>

<script type="text/javascript">
function addLoadEvent(fn) {var oldEvent = window.onload;if(typeof window.onload != 'function') {window.onload = fn;}else {window.onload = function() {oldEvent();fn();}}
}
function fn1() {alert('加载一');
}
function fn2() {alert('加载二');
}
function fn3() {alert('加载三');
}
addLoadEvent(fn1);
addLoadEvent(fn2);
addLoadEvent(fn3);
</script>

<script type="text/javascript">
// 被刷油漆者
Decoratee = function() {alert('被刷油漆');
}
// 刷油漆工
Decorator = {beginList: [],    // 前置函数列表endList: [],    // 后置函数列表append: function(fn) {this.endList.push(fn);},before: function(fn) {this.beginList.splice(0, 0, fn);},wrap: function(fn/* 要被修饰的函数体 */) {var $ = this, $1 = [], $2 = [];// 包装前置函数for(var i = 0, len = $.beginList.length; i < len; i++) {$1[i] = $.beginList[i];}// 包装后置函数for(var i = 0, len = $.endList.length; i < len; i++) {$2[i] = $.endList[i];}try {return function(){for(var i = 0, len = $1.length; i < len; i++) {$1[i]();}if(typeof fn == 'function') fn();for(var i = 0, len = $2.length; i < len; i++) {$2[i]();}}}finally {this.beginList.length = this.endList.length = 0;}}
}Decorator.before(function() { alert('刷油漆前先钉木头') });
Decorator.before(function() { alert('刷油漆前先钉钉子') });
Decorator.append(function() { alert('刷油漆后要晾干') });
Decorator.append(function() { alert('刷油漆后要涂鸦') });
Decorator.wrap(Decoratee)(); // 开始刷油漆
</script>