javascript onclick，匿名函数

发布于 2024-07-25 08:08:19 字数 3331 浏览 7 评论 0原文

我是一名初级 JavaScript 程序员。我正在尝试创建类似于 Lightbox 2 的东西，但更简单。我想自己从头开始做的唯一原因是为了我可以学习。然而，我一直停留在显示图像的最后一个关键部分。我相信问题出在我尝试使用 onclick 并分配给匿名函数的地方：elem[i].onclick = function (){liteBoxFocus(imgSource,imgTitle); 返回假；}； 。如果您运行我的代码并尝试单击谷歌徽标，它将显示雅虎徽标和标题，而不是谷歌的徽标和标题。然而，当您单击雅虎徽标时，它工作正常，因此似乎匿名函数仅适用于最后一个循环。提前致谢！！！

为了您的方便，我已将整个 CSS/JS/XHTML 放在一页中。

<html>
<head>
<title>Erik's Script</title>

<style type="text/css">
#liteBoxBg, #liteBox {
    display: none;
}

#liteBoxBg {
    background-color: #000000;
    height: 100%;
    width:100%;
    margin:0px;
    position: fixed;
    left:0px;
    top: 0px;
    filter:alpha(opacity=80);
    -moz-opacity:0.8;
    -khtml-opacity: 0.8;
    opacity: 0.8;
    z-index: 40;
}

#liteBox {
    background-color:#fff;
    padding: 10px;
    position:absolute;
    top:10%;
    border: 1px solid #ccc;
    width:auto;
    text-align:center;
    z-index: 50;
}
</style>

<script type="text/javascript">

window.onload = start;

function start(){

    var imgTitle = "No title";
    var imgSource;
    var elem = document.getElementsByTagName("a");
    var i;

    //Dynamically insert the DIV's to produce effect
    var newDiv = document.createElement('div');
    newDiv.setAttribute("id", "liteBox");
    document.getElementsByTagName("body")[0].appendChild(newDiv);

    newDiv = document.createElement('div');
    newDiv.setAttribute("id", "liteBoxBg");
    document.getElementsByTagName("body")[0].appendChild(newDiv);

    //Check those anchors with rel=litebox
    for(i = 0;i < elem.length;i++){
        if(elem[i].rel == "litebox"){
            imgSource = elem[i].href.toString();
            imgTitle = elem[i].title;
            elem[i].childNodes[0].style.border="0px solid #fff";
            elem[i].onclick = function (){liteBoxFocus(imgSource,imgTitle); return false;};
        }
    }

    //When foreground is clicked, close lite box
    document.getElementById("liteBoxBg").onclick = liteBoxClose;
}

//Brings up the image with focus
function liteBoxFocus(source,title){
    document.getElementById("liteBox").style.display = "block";
    document.getElementById("liteBox").innerHTML = "<h1>" + title + "</h1>" +
                                                   "<img src='" + source + "'/><br />" +
                                                   "<a href='#' onclick='liteBoxClose();'><img src='images/litebox_close.gif' border='0' alt='close'/></a>";
    document.getElementById("liteBoxBg").style.display = "block";
}

//closes lite box
function liteBoxClose(){
    document.getElementById("liteBox").style.display = "none";
    document.getElementById("liteBoxBg").style.display = "none";
    return false;
}

</script>



</head>

<body>

<a href="http://www.google.com/intl/en_ALL/images/logo.gif" rel="litebox" title="Google Logo"><img src="http://www.google.com/intl/en_ALL/images/logo.gif" alt="" /></a>

<a href="
http://www.barbariangroup.com/assets/users/bruce/images/0000/4121/yahoo_logo.jpg" rel="litebox" title="Yahooo Logo"><img src="
http://www.barbariangroup.com/assets/users/bruce/images/0000/4121/yahoo_logo.jpg" alt="" /></a>



</body>
</html>

原文

I am a beginning javascript programmer. I am trying to create something similar to Lightbox 2, but much simpler. The only reason why I want to do it from scratch on my own is so that I can learn. However, I've been stuck on the last critical part where it displays the image. I believe the problem lies where I try to use onclick with assignment to an anonymous function:elem[i].onclick = function (){liteBoxFocus(imgSource,imgTitle); return false;};
. If you run my code and try clicking on the google logo it'll bring up the yahoo logo and title instead of google's logo and title. However when you click on the yahoo logo it works fine so it seems that the anonymous function only holds for the last loop. Thanks in advance!!!

I have placed the entire CSS/JS/XHTML in one page for your convenience.

<html>
<head>
<title>Erik's Script</title>

<style type="text/css">
#liteBoxBg, #liteBox {
    display: none;
}

#liteBoxBg {
    background-color: #000000;
    height: 100%;
    width:100%;
    margin:0px;
    position: fixed;
    left:0px;
    top: 0px;
    filter:alpha(opacity=80);
    -moz-opacity:0.8;
    -khtml-opacity: 0.8;
    opacity: 0.8;
    z-index: 40;
}

#liteBox {
    background-color:#fff;
    padding: 10px;
    position:absolute;
    top:10%;
    border: 1px solid #ccc;
    width:auto;
    text-align:center;
    z-index: 50;
}
</style>

<script type="text/javascript">

window.onload = start;

function start(){

    var imgTitle = "No title";
    var imgSource;
    var elem = document.getElementsByTagName("a");
    var i;

    //Dynamically insert the DIV's to produce effect
    var newDiv = document.createElement('div');
    newDiv.setAttribute("id", "liteBox");
    document.getElementsByTagName("body")[0].appendChild(newDiv);

    newDiv = document.createElement('div');
    newDiv.setAttribute("id", "liteBoxBg");
    document.getElementsByTagName("body")[0].appendChild(newDiv);

    //Check those anchors with rel=litebox
    for(i = 0;i < elem.length;i++){
        if(elem[i].rel == "litebox"){
            imgSource = elem[i].href.toString();
            imgTitle = elem[i].title;
            elem[i].childNodes[0].style.border="0px solid #fff";
            elem[i].onclick = function (){liteBoxFocus(imgSource,imgTitle); return false;};
        }
    }

    //When foreground is clicked, close lite box
    document.getElementById("liteBoxBg").onclick = liteBoxClose;
}

//Brings up the image with focus
function liteBoxFocus(source,title){
    document.getElementById("liteBox").style.display = "block";
    document.getElementById("liteBox").innerHTML = "<h1>" + title + "</h1>" +
                                                   "<img src='" + source + "'/><br />" +
                                                   "<a href='#' onclick='liteBoxClose();'><img src='images/litebox_close.gif' border='0' alt='close'/></a>";
    document.getElementById("liteBoxBg").style.display = "block";
}

//closes lite box
function liteBoxClose(){
    document.getElementById("liteBox").style.display = "none";
    document.getElementById("liteBoxBg").style.display = "none";
    return false;
}

</script>



</head>

<body>

<a href="http://www.google.com/intl/en_ALL/images/logo.gif" rel="litebox" title="Google Logo"><img src="http://www.google.com/intl/en_ALL/images/logo.gif" alt="" /></a>

<a href="
http://www.barbariangroup.com/assets/users/bruce/images/0000/4121/yahoo_logo.jpg" rel="litebox" title="Yahooo Logo"><img src="
http://www.barbariangroup.com/assets/users/bruce/images/0000/4121/yahoo_logo.jpg" alt="" /></a>



</body>
</html>

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风情万种。 2024-08-01 08:08:19

您的事件处理程序形成一个闭包，该闭包会记住指向封闭范围内的变量的“实时”指针。因此，当它们实际执行时，它们具有 imgSource 和 imgTitle 的最后一个值。

相反，您可以使用此模式来本地化变量值。这将在每次调用 getClickHandler 时在 getClickHandler 中创建源和标题的副本。因此，返回的函数会记住该循环迭代中的值。

//Check those anchors with rel=litebox
for(i = 0;i < elem.length;i++){
    if(elem[i].rel == "litebox"){
        imgSource = elem[i].href.toString();
        imgTitle = elem[i].title;
        elem[i].childNodes[0].style.border="0px solid #fff";
        elem[i].onclick = getClickHandler(imgSource, imgTitle);
    }
}


//Brings up the image with focus
function getClickHandler(source,title){
    return function() {
        document.getElementById("liteBox").style.display = "block";
        document.getElementById("liteBox").innerHTML = "<h1>" + title + "</h1>" +
                                               "<img src='" + source + "'/><br />" +
                                               "<a href='#' onclick='liteBoxClose();'><img src='images/litebox_close.gif' border='0' alt='close'/></a>";
        document.getElementById("liteBoxBg").style.display = "block";
    }
}

Your event handlers form a closure that remember a "live" pointer to the variables in the enclosing scope. So when they are actually executed, they have the last value imgSource and imgTitle had.

Instead, you can use this pattern to localize the variable values. This will create copies of source and title inside getClickHandler each time it is called. The returned function hence remembers the values in that iteration of the loop.

//Check those anchors with rel=litebox
for(i = 0;i < elem.length;i++){
    if(elem[i].rel == "litebox"){
        imgSource = elem[i].href.toString();
        imgTitle = elem[i].title;
        elem[i].childNodes[0].style.border="0px solid #fff";
        elem[i].onclick = getClickHandler(imgSource, imgTitle);
    }
}


//Brings up the image with focus
function getClickHandler(source,title){
    return function() {
        document.getElementById("liteBox").style.display = "block";
        document.getElementById("liteBox").innerHTML = "<h1>" + title + "</h1>" +
                                               "<img src='" + source + "'/><br />" +
                                               "<a href='#' onclick='liteBoxClose();'><img src='images/litebox_close.gif' border='0' alt='close'/></a>";
        document.getElementById("liteBoxBg").style.display = "block";
    }
}

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