settimeout调用的函数未结束

问题：在幻灯片中，下面的fade函数一直在调用fadin/out函数，请JsFiddle并运行大约十秒钟以查看问题。在IE中不起作用，不要让jsfiddle运行太久，它可能会使你的浏览器崩溃！

Js报价：http://jsfiddle.net/HdYmH/

详细信息（对于那些感兴趣的人）：嗨，很抱歉发布了一个有这么大代码块的问题。我还在学习javascript，并试图弄清楚如何制作幻灯片。我知道有很多js幻灯片，但我想把它作为一种学习体验。因此，请注意，此代码的某些部分非常糟糕。这个问题可能与幻灯片的changeSlide（）方法有关。

我使用firebug来找出哪种方法在几秒钟后被调用得最明显。out将被调用20k多次：|

// Generic fade function that fades in or out
function fade(pElem, pStartOpac, pEndOpac, fps, sec) {
    if ((typeof (pElem) !== "string") || (typeof (pStartOpac) !== "number")
            || (typeof (pEndOpac) !== "number") || (typeof (fps) !== "number")
            || (typeof (sec) !== "number")) {
        console.log("Parameters incorrect format has to be (string) Element Id, (double) Starting Opacity, (double) End Opacity, (integer) frames per second, (integer) seconds to run");
        return;
    }
    // The CSS opacity property only works from 1 to 0
    if (pStartOpac < 0) {
        pStartOpace = 0;
    }
    if (pStartOpac > 1) {
        pStartOpac = 1;
    }
    if (pEndOpac < 0) {
        pEndOpac = 0;
    }
    if (pEndOpac > 1) {
        pEndOpac = 1;
    }
    // Stop the fps from going over 60 or under 1 (The eye will barely notice
    // improvements above 60fps and fractional fps are not supported)
    if (fps > 60) {
        fps = 60;
    }
    if (fps < 1) {
        fps = 1;
    }
    var totalFrames = (fps * sec);
    var opacityChangePerSecond = (Math.abs(pStartOpac - pEndOpac) / sec);
    var opacityChangePerFrame = (opacityChangePerSecond / fps);
    var timeOutInterval = 1000 * (1 / fps);
    // console.log("totalFrames: "+totalFrames);
    // console.log("Opacity change per second: " + opacityChangePerSecond);
    // console.log("Opacity change per frame: " + opacityChangePerFrame);
    // console.log("Time out interval: " + timeOutInterval + " milliseconds");
    var opacity = pStartOpac;
    var timeoutVar;
    var elemId = document.getElementById(pElem);
    elemId.style.opacity = opacity;
    if (pStartOpac < pEndOpac) {
        fadeIn();
        return;
    } else {
        fadeOut();
        return;
    }
    function fadeIn() {
        opacity = opacity + opacityChangePerFrame;
        if (opacity > pEndOpac) {
            clearTimeout(timeoutVar);
            return;
        }
        elemId.style.opacity = opacity;
        timeoutVar = setTimeout(fadeIn, timeOutInterval);
        return;
    }
    function fadeOut() {
        if (opacity < pEndOpac) {
            clearTimeout(timeoutVar);
            return;
        }
        opacity = opacity - opacityChangePerFrame;
        if (opacity < 0) {
            opacity = 0;
        }
        elemId.style.opacity = opacity;
        timeoutVar = setTimeout(fadeOut, timeOutInterval);
        return;
    }
}