ผมเขียน Dropdown List เชื่อมกับ JQuery แล้วรู้สึกมันแปลกไม่กระชับ ช่วยแนะนำวิธีที่ถูกต้องให้หน่อยครับ

<script type="text/javascript">
	function txtboxToggleAir1(str){
		if (str=="1"){
			document.getElementById("air1t").disabled  = false;
			document.getElementById("air1h").disabled  = false;
		}else{
			document.getElementById("air1t").disabled  = true;
			document.getElementById("air1h").disabled  = true;
		}
	}

	function txtboxToggleAir2(str){
		if (str=="on"){
			document.getElementById("air2t").disabled  = false;
			document.getElementById("air2h").disabled  = false;
		}
		if(str=="off"){
			document.getElementById("air2t").disabled  = true;
			document.getElementById("air2h").disabled  = true;
		}
	}

Air1: <br>
	<select name="air1" onchange="txtboxToggleAir1(this.value)">
	  	<option value="2">......</option>
	    <option value="1">On</option>
	    <option value="2">Off</option>
  	</select>

    <input type="text" name="air1t" id="air1t" value="" />
    <input type="text" name="air1h" id="air1h" value="" />

    <br><br>

Air2: <br>
	<select name="air2" onchange="txtboxToggleAir2(this.value)">
	  	<option value="2">......</option>
	    <option value="on">On</option>
	    <option value="off">Off</option>
  	</select>

    <input type="text" name="air2t" id="air2t" value="" />
    <input type="text" name="air2h" id="air2h" value="" />

<script src="http://code.jquery.com/jquery-1.8.3.js "></script>
<script type="text/javascript">
$(document),ready(function(){
	$("select.air").change(function(){
		var prefix = $(this).attr("name");        
		if($("option:selected",this).val() == 2){
			$("input#"+prefix+"t ,input#"+prefix+"h").val('0').prop("readonly",true).css("color","gray");
	        }else{
			$("input#"+prefix+"t ,input#"+prefix+"h").val('').prop("readonly",false).css("color","black");
		}
	});
});
</script>	

Air1: <br>
	<select name="air1"  class="air">
  	<option>......</option>
	<option value="1">On</option>
	<option value="2">Off</option>
  	</select>

    <input type="text" name="air1t" id="air1t" value="" />
    <input type="text" name="air1h" id="air1h" value="" />

    <br><br>

Air2: <br>
	<select name="air2" class="air">
	  <option>......</option>
	  <option value="1">On</option>
	  <option value="2">Off</option>
  	</select>

    <input type="text" name="air2t" id="air2t" value="" />
    <input type="text" name="air2h" id="air2h" value="" />