js 复选框

for(var i=0;i<listsize;i++){
var dri=document.getElementsByName("checkbox"+i);
var id=document.getElementById('id'+i).value;
test+=id+"_";
alert(dri.length);
for(i=0;i<dri.length;i++){
if(dri[i].checked){
test+=dri[i].value+",";
}
}
test+=";";
}
一般用属性getElementsByName，