create unique id with javascript

Question

I have a form where a user can add multiple select boxes for multiple cities. The problem is that each newly generated select box needs to have a unique id. Can this be done is JavaScript?

UPDATE: here is the part of the form for selecting cities. Also note that i'm using some php to fill in the cities when a specific state is selected.

<form id="form" name="form" method="post" action="citySelect.php">
<select id="state" name="state" onchange="getCity()">
    <option></option>
    <option value="1">cali</option>
    <option value="2">arizona</option>
    <option value="3">texas</option>
</select>
<select id="city" name="city" style="width:100px">

</select>

    <br/>
</form>

Here is the javascript:

$("#bt").click(function() {

$("#form").append(
       "<select id='state' name='state' onchange='getCity()'>
           <option></option>
           <option value='1'>cali</option>
           <option value='2'>arizona</option>
           <option value='3'>texas</option>
        </select>
        <select id='city' name='city' style='width:100px'></select><br/>"
     );
});

Answer 1

another way it to use the millisecond timer:

var uniq = 'id' + (new Date()).getTime();