HTML ->
<div class="select">
<div class="input-wrapper">
<input type="text" id="theText" />
</div>
<div class="options">
<select>
<option value="1"> One </option>
<option value="2"> Two </option>
</select>
</div>
</div>
CSS ->
.select{
border:1px solid rgb(230,230,230);
width:165px;
height:25px;
position:relative;
background:;
}
.input-wrapper{
position:absolute;
top:0;
width:135px;
height:25px;
overflow:hidden;
z-index:10;
}
input{
border:none;
padding:0;
margin:0;
width:135px;
}
.options{
position:absolute;
top:-2px;
left:-2px;
display:none;
width:164px;
border-top:none;
background:#fff;
z-index:0;
}
.options select{
width:189px;
min-height:26px;
border:1px solid rgb(230,230,230);
}
ちょっとした jQuery 風味 ->
$('.select input').on('keyup', function(){
$('.options').show();
});
$('select').on('change', function(){
$('.options').hide();
});