用于深山在线投票的一个javascript统计checkbox现在选中的个数一边点复选框一边验证并计算现在选了多少个复选框

以下为详细代码

用在深山在线投票系统里面的用javascript统计checkbox选中个数

<form method="post" action="">
<label for="id[]100"><input type="checkbox" name="id[]" id="id[]100" onClick="docheck(this,'','','','')" value="100" /><span>选择</span></label>
<label for="id[]99"><input type="checkbox" name="id[]" id="id[]99" onClick="docheck(this,'','','','')" value="99" /><span>选择</span></label>
<label for="id[]98"><input type="checkbox" name="id[]" id="id[]98" onClick="docheck(this,'','','','')" value="98" /><span>选择</span></label>
<label for="id[]97"><input type="checkbox" name="id[]" id="id[]97" onClick="docheck(this,'','','','')" value="97" /><span>选择</span></label>
<label for="id[]96"><input type="checkbox" name="id[]" id="id[]96" onClick="docheck(this,'','','','')" value="96" /><span>选择</span></label>
<label for="id[]95"><input type="checkbox" name="id[]" id="id[]95" onClick="docheck(this,'','','','')" value="95" /><span>选择</span></label>
<label for="id[]94"><input type="checkbox" name="id[]" id="id[]94" onClick="docheck(this,'','','','')" value="94" /><span>选择</span></label>
<label for="id[]93"><input type="checkbox" name="id[]" id="id[]93" onClick="docheck(this,'','','','')" value="93" /><span>选择</span></label>
<label for="id[]92"><input type="checkbox" name="id[]" id="id[]92" onClick="docheck(this,'','','','')" value="92" /><span>选择</span></label>
<label for="id[]91"><input type="checkbox" name="id[]" id="id[]91" onClick="docheck(this,'','','','')" value="91" /><span>选择</span></label>
<label for="id[]90"><input type="checkbox" name="id[]" id="id[]90" onClick="docheck(this,'','','','')" value="90" /><span>选择</span></label>
<label for="id[]89"><input type="checkbox" name="id[]" id="id[]89" onClick="docheck(this,'','','','')" value="89" /><span>选择</span></label>
</form>
<script>
toup_shaohit = 3; //最少个数
toup_hits = 5;  //最多个数
//在多选时，限制多选的个数
var num=0;
function docheck(obj,beizu2,beizu3,beizu4,beizu5){
 if(obj.checked==true){
  num++;
  }else{
  num--;
  }
 if (num>toup_hits){
  alert("最多只能选择 "+ toup_hits +" 项！");
  obj.checked=false;
  num--;
 }
}
</script>