function func33(){
document.getElementById("set1").options[0].removeNode(true);//删除第1个
document.getElementById("set1").options[document.getElementById("set1").length] = new Option("33", "3");}
<select name="set1" id="set1">
<option value="1">11</option>
<option value="1">22</option>
</select>
<input type="button" value="ADD option" onclick="func33()">
document.getElementById("set1").options[0].removeNode(true);//删除第1个
document.getElementById("set1").options[document.getElementById("set1").length] = new Option("33", "3");}
<select name="set1" id="set1">
<option value="1">11</option>
<option value="1">22</option>
</select>
<input type="button" value="ADD option" onclick="func33()">
解决方案 »
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