借助HTML5 Web Worker 解决资源预加载 的一些顽疾.

//反面教材. 
//script Element + link Element(FireFox加载HTML) + object ELement (FireFox  JS CSS ...)
//需要在恰当时间 调用dispose()方法用来 移除过多的节点.(受Firefox 和 Opera拖累)
void function (win,doc,head,ns){
     var _class = '__PRELOAD_CLEARTEMPELEMENTS__' , _tag = 'script';
     if(ns.preLoad){
          return;
     }
     var _preLoad = ns.singlePreLoad = !!doc.getBoxObjectFor || win.mozInnerScreenX != null ? (_tag = '*') && function(sURL,isHTML){
               //FF3.0+开始支持 object加载其他数据类型. 如果是html则会解析该html
               var el;
               if(isHTML){
                    el = doc.createElement('link');
                    el.type = 'text/css';
                    el.rel = 'stylesheet';
                    el.href = sURL;
               }else{
                    el = doc.createElement('object');
                    el.data = sURL;
               }
               el.className = _class;
               head.appendChild(el);
          }: function(sURL){//!FF
                    var el = doc.createElement('script');
                    el.type = 'text/C';
                    el.className = _class;
                    el.src = sURL;
                    head.appendChild(el);          
          };
     ns.preLoad = function(aURL){
          typeof aURL == 'string' && (aURL = [aURL]);
          for(var i = 0 , l = aURL.length ; i < l ; i++)_preLoad(aURL[i]);
     };
     ns.preLoad.dispose = function (){
          var list = ns.DOM.$C('__PRELOAD_CLEARTEMPELEMENTS__',_tag,head);
          for (var i = list.length ; i-- ;){
               head.removeChild(list[i]);
          }
          list = null;
     };
          
}(window,document,document.getElementsByTagName('head')[0],Visit.Util);

//worker + script  方案
引入worker.js
onmessage = function(e){ 
    var a = e.data.toString().split(','); 
          for(var i = 0 , l = a.length ;i++){ 
               try{ 
                    //避免因加载失败导致脚本不在继续执行下去. 否则 一个imirtScripts.call(null,a); 就解决问题了.
                    //现在,还导致失去了并行加载的优势.但是也是在是木有办法.
                    importScripts(a[i]); 
               }catch(e){} 
          } 
    postMessage('Loaded'); 
};



void function (win,doc,head,ns){ 
     var _dom = ns.DOM, 
          _workerURL = 'js/worker.js',//worker.js Path 
          _emptyFn = function(){}; 
      
     if(ns.preLoad){ 
          return; 
     } 
     if(win.Worker){//FF3.5+ Opera10+  Safari4+ Chrome3+ (需要 worker.js支持) 
          ns.preLoad = function(aURL){ 
               var _w = new win.Worker(_workerURL); 
               _w.onerror = _emptyFn; 
               _w.onmessage = function(e){ 
                    e.data == 'loaded' && (_w.terminate(),1) && (_w = null);// 
               }; 
               _w.postMessage(aURL); 
          }; 
     }else if(!doc.getBoxObjectFor || !win.opera){//IE6+ Safari3- Chrome2- 
          ns.preLoad = function(aURL){ 
               for(var i = 0,l = aURL.length ; i < l ; i++){ 
                    _dom.loadJS(aURL[i],null,null,'text/C'); 
               } 
          }; 
           
     }else{//FF3.0-  Opera9.6- 
          ns.preLoad = _emptyFn; 
     } 
           
}(window,document,document.getElementsByTagName('head')[0],Visit.Util);