Value field name.
Examples
sample
<select id="dropdown" width="200"></select>
<script>
$('#dropdown').dropdown({
valueField: 'newValueField',
dataSource: [ { newValueField: 1, text: 'One' }, { newValueField: 2, text: 'Two' }, { newValueField: 3, text: 'Three' } ]
});
</script>