Question

问题：在幻灯片放映中，下面的淡入淡出功能一直调用淡入/淡出功能，请JsFiddle运行大约十秒钟才能看到问题。在IE中不起作用，不要让jsfiddle运行太长时间，它可能会使浏览器崩溃！

详细信息（对于那些感兴趣的人）：嗨，很抱歉用这么大的代码块发布问题。我还在学习javascript，并试图弄清楚如何制作幻灯片。我知道那里有很多js幻灯片，但我想把它想象成一种学习经历。因此请注意，此代码的某些部分非常糟糕。问题可能与幻灯片的changeSlide（）方法有关。

我使用firebug来找出几秒后最明显被调用的方法fadeOut将被称为20k +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;
    }

}

Answer 1

遇到问题：当不透明度变为＆lt; 0时，将其设置为0，然后执行：if (opacity < pEndOpac)。 pEndOpac为0，因此0 <0的计算结果为false，永远不会清除超时。解决方案是if (opacity <= pEndOpac)：

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;
}

settimeout调用的函数没有结束

1 个答案: