jQuery UI自动完成自动对焦不起作用

我正在使用jQuery UI自动完成功能，并尝试实现autoFocus选项.

I am using jQuery UI autocomplete and trying to implement the autoFocus option.

文档指出以下内容: 如果设置为true，则第一项将自动聚焦.

The documentation states the following: If set to true the first item will be automatically focused.

我创建了一个基本示例，但无法正常工作.我肯定想念一些明显的东西.参见此处: http://jsfiddle.net/9bQJX/

I created a basic example and cannot get to work. I must be missing something obvious. See here: http://jsfiddle.net/9bQJX/

$("#autocomplete").autocomplete({
    source: [
        "ActionScript",
        "AppleScript",
        "Asp",
        "BASIC",
        "C",
        "C++",
        "Clojure",
        "COBOL",
        "ColdFusion",
        "Erlang",
        "Fortran",
        "Groovy",
        "Haskell",
        "Java",
        "JavaScript",
        "Lisp",
        "Perl",
        "PHP",
        "Python",
        "Ruby",
        "Scala",
        "Scheme"
    ],
    autoFocus: true
});