不能清空,但可以设置为指定的选项。
<select id="demo">
<option value="1">111</option>
<option value="2">222</option>
</select><button id="btn">设置为默认值</button>
<script type="text/javascript">
document.getElementById('btn').onclick = function() { document.getElementById('demo').selectedIndex = 0; }
</script>
<select id="demo">
<option value="1">111</option>
<option value="2">222</option>
</select><button id="btn">设置为默认值</button>
<script type="text/javascript">
document.getElementById('btn').onclick = function() { document.getElementById('demo').selectedIndex = 0; }
</script>
<select id="demo">
<option value="1">111</option>
<option value="2">222</option>
</select><button id="btn">设置为默认值</button>
<script type="text/javascript">
document.getElementById('btn').onclick = function() { document.getElementById('demo').innerHTML=""; }
</script>
var ter= document.getElementById("term"); ter.length=1; //重新新加
//ter.options.add(new Option("12个月","12"));
//ter.options.add(new Option("24个月","24"));
//ter.options.add(new Option("36个月","36"));
//ter.options.add(new Option("48个月","48"));
//ter.options.add(new Option("60个月","60"));
obj.options.length=0;
obj.options.add(new Option("请选择","0"));
<select id="demo">
<option value="1">111</option>
<option value="2">222</option>
</select>