javascript body.scrollTop vs documentElement.scrollTop vs window.pageYOffset vs window.scrollY
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body.scrollTop vs documentElement.scrollTop vs window.pageYOffset vs window.scrollY
提问by Himanshu P
When trying to find out how much a web page has been scrolled from the top, which of these should one use:
当试图找出一个网页从顶部滚动了多少时，应该使用以下哪一个：
document.body.scrollTop,
document.body.scrollTop,
document.documentElement.scrollTop,
document.documentElement.scrollTop,
window.pageYOffset,
window.pageYOffset,
window.scrollY
window.scrollY
Which one(s) would I choose in these 2 separate scenarios:
在这 2 个不同的场景中，我会选择哪一个：
a) If I wanted maximum compatibility (across the main browsers used currently)?
a) 如果我想要最大的兼容性（跨当前使用的主要浏览器）？
b) If I wanted code that was most standards compliant/future-proof/strict-mode-compatible (but didn't care about supporting old/non-standard browsers)?
b) 如果我想要大多数标准兼容/面向未来/严格模式兼容的代码（但不关心支持旧的/非标准浏览器）？
回答by Prinzhorn
I'm using three of them in the skrollr source
我在 skrollr 源中使用了其中的三个
return window.pageYOffset || document.documentElement.scrollTop || document.body.scrollTop || 0;
a) So far it's working across all browsers (nobody complaint in the past year).
a) 到目前为止，它适用于所有浏览器（过去一年没有人抱怨）。
b) Since it will use the first one that is defined, I guess it's pretty future proof and stable.
b）由于它将使用定义的第一个，我想它是未来证明和稳定的。
If you're fancy you could do this as well
如果你喜欢你也可以这样做
Math.max(window.pageYOffset, document.documentElement.scrollTop, document.body.scrollTop)
回答by jasonklein
Given that skrollr does not use window.scrollY, this may have been obvious, but as further answer to the original question: window.pageYOffsetis an alias for window.scrollY. See Window.scrollY.
鉴于 skrollr 不使用window.scrollY，这可能是显而易见的，但作为对原始问题的进一步回答：window.pageYOffsetis an alias for window.scrollY. 请参阅Window.scrollY。
回答by Tom
To Prinzhorn's answear:
对Prinzhorn的回答：
Since bodyand documentElementis undefinedin Chrome/Firefox, better use:
由于body和documentElement是undefined在Chrome / Firefox中，更好地利用：
return window.pageYOffset || document.documentElement.scrollTop || document.body.scrollTop || 0;
Tested myself.
本人测试过。
回答by yaya
Chrome uses documentElement.scrollTop, firefox uses body.scrollTop
Chrome 使用documentElement.scrollTop，firefox 使用body.scrollTop
