在Javascript行为不规律的情况下在两种状态之间应用转换

Question

我很难理解为什么过渡不像预期的那样。它应该应用"from"，然后将"transition"添加到"el"，然后它应该运行"to"，最后onTransitionEnd它应该运行"callback"(前缀为清除过渡属性的代码)。

在Webkit浏览器中，它可以正确地转换slideDown，但是slideUp是即时的。

尔格?

JSFiddle: http://jsfiddle.net/enhTd/

var $ = function(query) {
                var a = [],
                    n = document.querySelectorAll(query),
                    l = n.length;
                for( var i = 0; i<l; i++){
                    a.push(n[i]);
                    }
                if(l>1) {return a;} else {return a[0];}
                },
    $id = function(query) { return document.getElementById(query);},
    getSupportedPropertyName = function(properties) {
        for (var i = 0; i < properties.length; i++) {
            if (typeof document.body.style[properties[i]] != "undefined") {
                return properties[i];
            }
        }
        return null;
    },
    vendorTransitions = ["transition", "msTransition", "webkitTransition", "MozTransition", "OTransition"],
    prefixedTransitionProperty = getSupportedPropertyName(vendorTransitions),
    transition = function(opts){
        opts.from && opts.from();
        if(prefixedTransitionProperty){
            var c = opts.callback || function() {},
                el = opts.el,
                cb = function(event){
                    var ev = event, callback = c;
                    ev.target.removeEventListener(prefixedTransitionProperty+"End", cb);
                    ev.target.style[prefixedTransitionProperty] = "none";
                    if(callback) {
                        callback(ev);
                        }
                    };
            el.style[prefixedTransitionProperty] = opts.transition || "";
            el.addEventListener(prefixedTransitionProperty+"End", cb);
        }
        opts.to && opts.to();
    },
    slideDown = function(el, t){
        var style = el.style,
            h, oh = el.offsetHeight,
            t = t || 1000;
        //Grab real height
        style.height = "";
        h = el.offsetHeight;
        transition({
            "el": el,
            transition: "height "+t+"ms ease",
            from: function() {
                style.height = oh+"px";
            },
            to: function(){
                style.overflow = "hidden";
                style.height = h+"px";
                },
            callback: function(event){
                event.target.style.height = "";
                }
            });

    },
    slideUp = function(el, t){
        var style = el.style,
            h = el.offsetHeight,
            t = t || 1000;
        transition({
            "el": el,
            transition: "height "+t+"ms ease",
            from: function() {
                style.height = h+"px";
                },
            to: function(){
                style.overflow = "hidden";
                style.height = "0";
                }
            });
    },
    slideToggle = function(el, t){
        var t = t || 1000;
        if(el.style.height=="0px"){
            slideDown(el, t);
        } else {
            slideUp(el, t);
        }
    };

slideUp($id("intro"));
$("a[href='#intro']").forEach(function(el){
    el.addEventListener("click", function(ev) { 
        ev.preventDefault();
        if(ev.target.classList.contains("hide")){
            slideUp($(ev.target.hash));
        } else {
            slideDown($(ev.target.hash));
        }
    });
});
$("li h3").forEach(function(el){
    el.addEventListener("click", function(ev) { 
        ev.preventDefault();
        slideToggle(ev.target.parentNode);
    });
});

Answer 1

在某些浏览器中，您不能仅仅设置初始状态，设置最终状态并期望CSS转换工作。

相反，必须设置初始状态，然后在设置最终状态并期望转换运行之前必须呈现它。使其呈现的最简单方法是返回到事件循环，然后在setTimeout()调用后执行任何进一步处理(如设置最终状态)。

Answer 2

试试这个:http://jsfiddle.net/enhTd/1/(在chrome和ff中测试)

first:做jfriend00所说的:

在你的过渡函数:

transition = function (opts) {
    ..
    setTimeout(function() {
        opts.to && opts.to();
    }, 1)
}

second: slideDown()方法中不需要回调:

slideDown = function (el, t) {
    ..
    take this out:
      /*callback: function (event) {
            event.target.style.height = "";
        }*/
    });

从设计的角度来看…回调函数没有添加任何值。当涉及到过渡时，你应该从你离开的地方继续。

third: disable slide down when slide already down. 但是我把它留给你。