在jQuery UI滑块上创建事件时不可用的值?

$('#foo').slider({
  range: 'min',
  min: 0,
  max: 1000,
  step: 100,
  value: 500,
  create: function( event, ui) {
          var bar = ui.value;
  },
  //etc...
});
$('#foo').slider({
  range: 'min',
  min: 0,