checkbox全选，反选，选特定的值

<script type="text/javascript">

var tem = ""; 
var temp = "";
function checkId(e,itemName,numvalue,namevalue) 
{ 

var arrayid=document.getElementById('mem'); 

if(e.checked==true){
tem += numvalue+",";

} else{
index=tem.indexOf(","+numvalue+",");
    tem1=tem.substr(0,index+1);
    
    tem2=tem.substr(index+(","+numvalue+",").length);  
      
        tem=tem1+tem2;
   
} 
    if(tem == ""){
      arrayid.value=tem;   
    }else{
      arrayid.value=","+tem;
    }

} 

function uncheckAll() {