select根據值動態改變選中項

<script language="javascript">
	//根據option的value值修改select的默認選項
	function selectValues(obj,v){
	  if(obj!=null && v!=null){
		for (var i = 0; i < obj.options.length; i++) {
		  if (obj.options(i).value==v) {
			obj.selectedIndex=i; break;
		  }
		}
	  }
	}
	
	function fun1(){
		var val = document.getElementById("Tyear").value;
		var obj = document.getElementById("year");
		selectValues(obj,val);
	}
</script>

<input  type="text" value="2020" id="Tyear"/><input type="button" οnclick="fun1()" value="確定"/>
<br />
<select id="year" name="year" >
     <option value="2013" >2013</option>
     <option value="2014" selected="selected">2014</option>
     <option value="2015" >2015</option>
     <option value="2016" >2016</option>
     <option value="2017" >2017</option>
     <option value="2018" >2018</option>
     <option value="2019" >2019</option>
     <option value="2020" >2020</option>
</select>