JavaScript 通过“类”来查找元素

 1     function $(name,id){
 2 
 3         // BUG Handle
 4         try{
 5             if(!Boolean(name) || /^\s*$/.test(name)){
 6                 throw new Error(‘object not is empty or null‘);
 7             }
 8         }catch(e){
 9             alert(e);
10             return false;
11         }
12 
13         var elems=[],
14             reg = new RegExp(‘\\b‘+ name +‘\\b‘),
15             idx = 0;
16 
17         if(document.querySelectorAll){
18             elems = document.querySelectorAll(‘.‘+name);
19         }else if(id){
20             var childElements = document.getElementById(id).getElementsByTagName(‘*‘);
21             for(var i=0;i<childElements.length;i++){
22                 if(reg.test(childElements[i].className)){
23                     elems.push(childElements[i]);
24                 }
25             }
26         }else{    
27             var allElements = document.getElementsByTagName(‘*‘);
28             for(var i=0;i<allElements.length;i++){
29                 
30                 if(reg.test(allElements[i].className)){
31                     elems[idx] = allElements[i];
32                     idx++;
33                 }
34             }
35 
36         }
37 
38         if(elems.length==1){
39             return elems[0]
40         }else{
41             return elems;
42         }
43     }
44 
45 // 调用方法： $(className[,parentID])