Make your dialog first. Then make the selectmenus…
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8" />
<title>UI</title>
<meta http-equiv="X-UA-Compatible" content="IE=edge" />
<script>
$(function(){
$("fieldset").dialog()
$( "#speed" ).selectmenu();
$( "#files" ).selectmenu();
$( "#number" )
.selectmenu()
.selectmenu( "menuWidget" )
.addClass( "overflow" );
$( "#salutation" ).selectmenu();
})
</script>
<style>
fieldset {
border: 0;
}
label {
display: block;
margin: 30px 0 0 0;
}
.overflow {
height: 200px;
}
</style>
</head>
<body>
<fieldset>
<label for="speed">Select a speed</label>
<select name="speed" id="speed">
<option>Slower</option>
<option>Slow</option>
<option selected="selected">Medium</option>
<option>Fast</option>
<option>Faster</option>
</select>
<label for="files">Select a file</label>
<select name="files" id="files">
<optgroup label="Scripts">
<option value="jquery">jQuery.js</option>
<option value="jqueryui">ui.jQuery.js</option>
</optgroup>
<optgroup label="Other files">
<option value="somefile">Some unknown file</option>
<option value="someotherfile">Some other file with a very long option text</option>
</optgroup>
</select>
<label for="number">Select a number</label>
<select name="number" id="number">
<option>1</option>
<option selected="selected">2</option>
<option>3</option>
<option>4</option>
<option>5</option>
<option>6</option>
<option>7</option>
<option>8</option>
<option>9</option>
<option>10</option>
<option>11</option>
<option>12</option>
<option>13</option>
<option>14</option>
<option>15</option>
<option>16</option>
<option>17</option>
<option>18</option>
<option>19</option>
</select>
<label for="salutation">Select a title</label>
<select name="salutation" id="salutation">
<option disabled selected>Please pick one</option>
<option>Mr.</option>
<option>Mrs.</option>
<option>Dr.</option>
<option>Prof.</option>
<option>Other</option>
</select>
</fieldset>
</body>
</html>
JΛ̊KE