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javascript - 如何检测已加载新内容以响应滚动触发器?

转载 作者:行者123 更新时间:2023-11-30 17:27:05 24 4
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我在 Facebook 上运行一个脚本,要求我在我的“ friend ”窗口中获取人们的 ID(这可能不是完成此特定任务的最有效方法,但因为我想知道如何一般来说,这是一个很好的例子)。

这意味着如果我的好友数量较多,我必须向下滚动 Facebook 才能将他们添加到页面。

我添加了将页面向下滚动到页脚的逻辑,但我不知道如何强制获取 ID 的函数在内容加载后运行。

现在,我已经使用了 setTimeout 几秒钟 - 显然,这不能保证在适当的时间,所以我想知道如何正确地做到这一点:

var k;
function doit(){

k = document.getElementsByClassName("_698");

var g= Array.prototype.slice.call(k);
confirm(g.length);
// the confirm is just to make sure it's working
// (if i don't use setTimeout it'll return a smaller number
// since not all the friends were included)

}

window.addEventListener("load", function(){
document.getElementById( "pageFooter" )
.scrollIntoView();setTimeout(doit,3000);
});

最佳答案

Crayon Violent 在 his answer to JavaScript detect an AJAX event 中详细介绍了如何完成此操作.诀窍是 Hook 底层 XMLHttpRequest 对象,以便检测何时发送请求。

我已经重新编写了一些逻辑以使其更适合您的需求:

//
// Hooks XMLHttpRequest to log all AJAX requests.
// Override ajaxHook.requestCompleted() to do something specific
// in response to a given request.
//
var ajaxHook = (function()
{
// we're using a self-executing function here to avoid polluting the global
// namespace. The hook object is returned to expose just the properties
// needed by client code.
var hook = {
// by default, just logs all requests to the console.
// Can be overridden to do something more interesting.
requestCompleted: function(xmlHttp, url, method) { console.log(url); }
};

// hook open() to store URL and method
var oldOpen = XMLHttpRequest.prototype.open;
XMLHttpRequest.prototype.open = function(method, url)
{
this.hook_method = method;
this.hook_url = url;
oldOpen.apply(this, arguments);
}

// hook send() to allow hooking onreadystatechange
var oldSend = XMLHttpRequest.prototype.send;
XMLHttpRequest.prototype.send = function()
{
var xmlhttp = this;

//hook onreadystatechange event to allow processing results
var oldReadyStateChange = xmlhttp.onreadystatechange;
xmlhttp.onreadystatechange = function()
{
oldReadyStateChange.apply(xmlhttp, arguments);

if ( this.readyState === 4 ) // completed
{
hook.requestCompleted(xmlhttp,
xmlhttp.hook_url, xmlhttp.hook_method);
}
};

oldSend.apply(this, arguments);
};

return hook;
})();

在您的用户脚本中加载这段代码后,您就可以按如下方式实现您的逻辑:

var k;
function doit()
{
k = document.getElementsByClassName("_698");

var g= Array.prototype.slice.call(k);
confirm(g.length);
}

window.addEventListener("load", function()
{
ajaxHook.requestCompleted = function(xmlhttp, url, method)
{
// is this the request we're interested in?
// (Facebook appears to load friends from a URL that contains this string)
if ( /AllFriendsAppCollectionPagelet/.test(url) )
{
// Facebook defers rendering the results here,
// so we just queue up scraping them until afterwards
setTimeout(doit, 0);
}
};

// trigger loading of more friends by scrolling the bottom into view
document.getElementById( "pageFooter" )
.scrollIntoView();
});

关于javascript - 如何检测已加载新内容以响应滚动触发器?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/24021826/

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