如何在页面加载时让jQuery的自动完成插件显示其下拉列表？

<link rel="stylesheet" href="https://code.jquery.com/ui/1.12.1/themes/base/jquery-ui.css"><script src="https://code.jquery.com/ui/1.12.1/jquery-ui.js"></script>

$(document).ready(function() {
  $('#my-autocomplete').autocomplete({
    source: ['apple', 'banana', 'orange', 'grape']
  });
});

$(document).ready(function() {
  $('#my-autocomplete').autocomplete({
    source: ['apple', 'banana', 'orange', 'grape'],
    minLength: 0
  }).focus(function() {
    $(this).autocomplete('search', '');
  });
});