js判断多个select值是否重复

HTML部分

<select name="guige[]" id="guige_1">
<option value="1">颜色</option>
<option value="2">来源地</option>
</select>

<select name="guige[]" id="guige_2">
<option value="1">颜色</option>
<option value="2">来源地</option>
</select>

<select name="guige[]" id="guige_3">  
<option value="1">颜色</option>
<option value="2">来源地</option>
</select>

js代码部分

function checkform(){
var v1="";
var v2="";
var group = document.getElementsByName('guige[]');
var len=group.length;
 for(var m=1; m<=len; m++){
   v1=document.getElementById("guige_" + m).value;
  for(var n=m+1; n<=len; n++){
   v2=document.getElementById("guige_" + n).value;
   if(v1==v2){
    alert("规格重复");
 return false;
   }
  }
 }
}