如何检测iframe何时已经加载 [英] How to detect when an iframe has already been loaded

问题描述

似乎 $（'＃someIframe'）。load（function（）{...}）如果在iframe有完成加载。那是对的吗？

It seems that $('#someIframe').load(function(){...}) won't fire if it is attached after the iframe has finished loading. Is that correct?

我真正希望拥有一个在iframe加载完成后总是被调用的函数。为了使这个更清楚，这里有两种情况：

What I'd really like is to have a function that is always called once when or after an iframe has loaded. To make this clearer, here are two cases:

• Iframe尚未加载：运行回调函数一旦加载，


• Iframe已经加载：立即运行回调。

• Iframe hasn't loaded yet: run a callback function once it loads.
• Iframe has already loaded: run the callback immediately.

我该怎么做？

推荐答案

我把头撞到墙上，直到我发现什么

I've banged my head against a wall until I found out what's happening here.

• 使用。如果iframe已经被加载（事件永远不会触发），load（）是不可能的。


• 使用 .ready（） / code>不支持iframe元素（参考），并将调用即使iframe尚未加载，立即回调


• 使用 postMessage 或在只有在进行控制时才有可能在


• 在容器上使用 $（window）.load（）也会等待其他资源加载，如图像和其他iframe如果您只想等待一个特定的iframe，那么这不是一个解决方案。


• 在Chrome中检查 readyState 是否为一个alredy已启动的onload事件没有意义，因为Chrome会使用约：空白空白页面初始化每个iframe。 readyState 可能是完成，但它不是 readyState 您希望的页面（ src 属性）。

• Using .load() isn't possible if the iframe has already been loaded (event will never fire)
• Using .ready() on an iframe element isn't supported (reference) and will call the callback immediately even if the iframe isn't loaded yet
• Using postMessage or a calling a container function on load inside the iframe is only possible when having control over it
• Using $(window).load() on the container would also wait for other assets to load, like images and other iframes. This is not a solution if you want to wait only for a specific iframe
• Checking readyState in Chrome for an alredy fired onload event is meaningless, as Chrome initializes every iframe with an "about:blank" empty page. The readyState of this page may be complete, but it's not the readyState of the page you expect (src attribute).

以下是必要的：

1. 如果iframe尚未加载，我们可以观察 .load（）事件


2. 如果iframe已经加载，我们需要检查 readyState


3. 如果 readyState 是完成，我们通常可以假设iframe已经被加载。但是，由于Chrome的上述行为，我们还需要检查是否是空页的 readyState


4. 如果是我们需要在一个间隔期间观察 readyState ，以检查实际文档（与src属性相关）是否完整

1. If the iframe is not loaded yet we can observe the .load() event
2. If the iframe has been loaded already we need to check the readyState
3. If the readyState is complete, we can normally assume that the iframe has already been loaded. However, because of the above-named behavior of Chrome we furthermore need to check if it's the readyState of an empty page
4. If so, we need to observe the readyState in an interval to check if the actual document (related to the src attribute) is complete

我用以下功能解决了这个问题。已经（蜕变为ES5）在

I've solved this with the following function. It has been (transpiled to ES5) successfully tested in

• Chrome 49


• Safari 5

• Chrome 49
• Safari 5
• Firefox 45
• IE 8, 9, 10, 11
• Edge 24
• iOS 8.0 ("Safari Mobile")
• Android 4.0 ("Browser")

从 jquery.mark 获取的功能

Function taken from jquery.mark

/**
 * Will wait for an iframe to be ready
 * for DOM manipulation. Just listening for
 * the load event will only work if the iframe
 * is not already loaded. If so, it is necessary
 * to observe the readyState. The issue here is
 * that Chrome will initialize iframes with
 * "about:blank" and set its readyState to complete.
 * So it is furthermore necessary to check if it's
 * the readyState of the target document property.
 * Errors that may occur when trying to access the iframe
 * (Same-Origin-Policy) will be catched and the error
 * function will be called.
 * @param {jquery} $i - The jQuery iframe element
 * @param {function} successFn - The callback on success. Will 
 * receive the jQuery contents of the iframe as a parameter
 * @param {function} errorFn - The callback on error
 */
var onIframeReady = function($i, successFn, errorFn) {
    try {
        const iCon = $i.first()[0].contentWindow,
            bl = "about:blank",
            compl = "complete";
        const callCallback = () => {
            try {
                const $con = $i.contents();
                if($con.length === 0) { // https://git.io/vV8yU
                    throw new Error("iframe inaccessible");
                }
                successFn($con);
            } catch(e) { // accessing contents failed
                errorFn();
            }
        };
        const observeOnload = () => {
            $i.on("load.jqueryMark", () => {
                try {
                    const src = $i.attr("src").trim(),
                        href = iCon.location.href;
                    if(href !== bl || src === bl || src === "") {
                        $i.off("load.jqueryMark");
                        callCallback();
                    }
                } catch(e) {
                    errorFn();
                }
            });
        };
        if(iCon.document.readyState === compl) {
            const src = $i.attr("src").trim(),
                href = iCon.location.href;
            if(href === bl && src !== bl && src !== "") {
                observeOnload();
            } else {
                callCallback();
            }
        } else {
            observeOnload();
        }
    } catch(e) { // accessing contentWindow failed
        errorFn();
    }
};

工作示例

由两个文件组成（index.html和iframe.html）：
index.html ：

<!doctype html>
<html>
<head>
    <meta charset="utf-8">
    <title>Parent</title>
</head>
<body>
    <script src="https://code.jquery.com/jquery-1.12.2.min.js"></script>
    <script>
        $(function() {

            /**
             * Will wait for an iframe to be ready
             * for DOM manipulation. Just listening for
             * the load event will only work if the iframe
             * is not already loaded. If so, it is necessary
             * to observe the readyState. The issue here is
             * that Chrome will initialize iframes with
             * "about:blank" and set its readyState to complete.
             * So it is furthermore necessary to check if it's
             * the readyState of the target document property.
             * Errors that may occur when trying to access the iframe
             * (Same-Origin-Policy) will be catched and the error
             * function will be called.
             * @param {jquery} $i - The jQuery iframe element
             * @param {function} successFn - The callback on success. Will 
             * receive the jQuery contents of the iframe as a parameter
             * @param {function} errorFn - The callback on error
             */
            var onIframeReady = function($i, successFn, errorFn) {
                try {
                    const iCon = $i.first()[0].contentWindow,
                        bl = "about:blank",
                        compl = "complete";
                    const callCallback = () => {
                        try {
                            const $con = $i.contents();
                            if($con.length === 0) { // https://git.io/vV8yU
                                throw new Error("iframe inaccessible");
                            }
                            successFn($con);
                        } catch(e) { // accessing contents failed
                            errorFn();
                        }
                    };
                    const observeOnload = () => {
                        $i.on("load.jqueryMark", () => {
                            try {
                                const src = $i.attr("src").trim(),
                                    href = iCon.location.href;
                                if(href !== bl || src === bl || src === "") {
                                    $i.off("load.jqueryMark");
                                    callCallback();
                                }
                            } catch(e) {
                                errorFn();
                            }
                        });
                    };
                    if(iCon.document.readyState === compl) {
                        const src = $i.attr("src").trim(),
                            href = iCon.location.href;
                        if(href === bl && src !== bl && src !== "") {
                            observeOnload();
                        } else {
                            callCallback();
                        }
                    } else {
                        observeOnload();
                    }
                } catch(e) { // accessing contentWindow failed
                    errorFn();
                }
            };

            var $iframe = $("iframe");
            onIframeReady($iframe, function($contents) {
                console.log("Ready to got");
                console.log($contents.find("*"));
            }, function() {
                console.log("Can not access iframe");
            });
        });
    </script>
    <iframe src="iframe.html"></iframe>
</body>
</html>

iframe.html ：

<!doctype html>
<html>
<head>
    <meta charset="utf-8">
    <title>Child</title>
</head>
<body>
    <p>Lorem ipsum</p>
</body>
</html>

您还可以更改 src 属性 index.html http://example.com/ 。只需玩它。

You can also change the src attribute inside index.html to e.g. "http://example.com/". Just play around with it.

这篇关于如何检测iframe何时已经加载的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！