Jquery lodash debounce 在匿名函数中不起作用

Hello I cannot seem to figure out why the debounce function works as expected when passed directly to a keyup event; but it does not work if I wrap it inside an anonymous function.

I have fiddle of the problem: http://jsfiddle.net/6hg95/1/

编辑:添加了我try 过的所有东西.

HTML

<input id='anonFunction'/>
<input id='noReturnAnonFunction'/>
<input id='exeDebouncedFunc'/>
<input id='function'/>
<div id='output'></div>

JAVASCRIPT

$(document).ready(function(){
    $('#anonFunction').on('keyup', function () {
        return _.debounce(debounceIt, 500, false); //Why does this differ from #function
    });
    $('#noReturnAnonFunction').on('keyup', function () {
        _.debounce(debounceIt, 500, false); //Not being executed
    });
    $('#exeDebouncedFunc').on('keyup', function () {
        _.debounce(debounceIt, 500, false)(); //Executing the debounced function results in wrong behaviour
    });
    $('#function').on('keyup', _.debounce(debounceIt, 500, false)); //This is working.
});

function debounceIt(){
    $('#output').append('debounced');
}

anonFunction and noReturnAnonFunction does not fire the debounce function; but the last function does fire. I do not understand why this is. Can anybody please help me understand this?

EDIT Ok, so the reason that the debounce does not happen in #exeDebouncedFunc (the one you refer) is because the function is executed in the scope of the anonymous function and another keyup event will create a new function in another anonymous scope; thus firing the debounced function as many times as you type something (instead of firing once which would be the expected behaviour; see beviour of #function)?

你能解释一下#anonFunction和#function的区别吗.这是否又是一个范围问题，为什么其中一个有效，而另一个无效？

EDIT个 好了，现在我明白为什么会发生这种事了.这就是为什么我需要将它包装在一个匿名函数中的原因:

小提琴:http://jsfiddle.net/6hg95/5/

HTML

<input id='anonFunction'/>
<div id='output'></div>

JAVASCRIPT

(function(){
    var debounce = _.debounce(fireServerEvent, 500, false);

    $('#anonFunction').on('keyup', function () {
        //clear textfield
        $('#output').append('clearNotifications<br/>');
        debounce();
    });

    function fireServerEvent(){
        $('#output').append('serverEvent<br/>');
    }
})();