jQuery如何“准备好文档"?功能正常吗? [英] How does jQuery's "document ready" function work?
问题描述
jQuery如何检查文档是否已加载?如何检查文档加载是否完成?
How is jQuery checking if the document is loaded? How it is checking that the document load is finished?
推荐答案
它们绑定到DOMContentLoaded事件(或在某些浏览器上为onreadystatechange).如果不支持DOMContentLoaded或由于其他原因不触发DOMContentLoaded，它们也可以回退到常规的load事件.在支持它的浏览器上，他们使用此调用:
They bind to the DOMContentLoaded event (or onreadystatechange on some browsers). They also have a fallback to the regular load event, in case the DOMContentLoaded isn't supported or not fired for other reasons. On browsers supporting it, they use this call:
document.addEventListener( "DOMContentLoaded", DOMContentLoaded, false );
在IE< 9上:
On IE <9:
document.attachEvent( "onreadystatechange", DOMContentLoaded);
这些调用中DOMContentLoaded的第二个实例是它们自己的函数-实际上是对源代码中bindReady上方的ready函数的引用.此功能将通过检查document.body来检查DOM树是否已完成.如果尚不存在，则等待一毫秒(使用setTimeout)，然后再次检查.当document.body存在时，它们遍历您设置的回调列表.
The second instance of DOMContentLoaded in these calls is their own function - actually a reference to the ready function right above bindReady in the source code. This function will check that the DOM tree is actually done by checking for document.body. If it doesn't exist yet, they wait a millisecond (using setTimeout) and check again. When document.body exists, they traverse the list of callbacks you've set.
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