JS做的全选和取消全选

-----------------------------html-----------------------------------------

<input type="checkbox" name="test"/>1
<input type="checkbox" name="test"/>2
<input type="checkbox" name="test" />3
<input type="checkbox" name="test" />4
<input type="checkbox" name="test" />5
<input type="checkbox" id="chooseall" onclick="selectAll()"/>全选

-------------------------js-----------------------------------

var chooseall=document.getElementById("chooseall"),
   mytest=document.getElementsByName("test"),
   leng=mytest.length;
function selectAll(){
   if(chooseall.checked==true){
      for(i=0;i<leng;i++){
         mytest[i].checked=true;
      }
   }else{
      for(i=0;i<leng;i++){
         mytest[i].checked=false;
      }
   }
}