สอบถามค่ะ ถ้า select เลือกค่าใดค่าหนึ่งแล้ว ให้check บนcheck box อัตโนมัติ ในหน้าเดิมอ่ะค่ะ

<script type="text/javascript">
function fncCheck(_val){
  var _chk = document.getElementsByName("chk_oper")
  var _len = _chk.length
  if(_val != ""){
    for(var i=0;i<_len;i++){
      if (_val == _chk[i].value){
      _chk[i].checked = true
	  }
	  else{
      _chk[i].checked = false
	  }
	}
  }
  else{
   for(var i=0;i<_len;i++){
      _chk[i].checked = false
	}
  }
}
</script>

<select id="chk_sup" onchange="fncCheck(this.value);">
<option value ="">SELECT</option>
<option value ="RED" >RED</option>
<option value ="YELLOW">YELLOW</option>
<option value ="ALL">ALL</option>
</select> 


<input type="checkbox" name="chk_oper" id="chk_oper" value="RED" />RED
<input type="checkbox" name="chk_oper" id="chk_oper" value="YELLOW" />YELLOW
<input type="checkbox" name="chk_oper" id="chk_oper" value="ALL" />ALL