你需要这样的东西吗?
HTML:
<select id="myselect">
<option value="volvo">Volvo</option>
<option value="saab">Saab</option>
<option value="mercedes">Mercedes</option>
<option value="audi">Audi</option>
</select>
<input id="newoption" type="text" />
<button id="check">Check</button>
jQuery:
$(document).ready(function() {
$("button#check").click(function() {
var newOpt = $("input#newoption").val();
$("#myselect option").each(function(){
var text = $(this).val();
if(newOpt.length>0 && text.indexOf(newOpt)!=-1){
console.log("already present!");
}
});
});
});
jsfiddle