Use of javascript scrollTop

Javascript scrollTop obtains the offset of the scroll bar relative to its top (for example, creating an automatically hidden "Back to Top" button ). In practical applications, you may encounter the following problems:
Document.doc umentElement. scrollTop is 0 in Chrome.
Document. body. scrollTop is always 0 in IE and firefox

1. Differences between windows. pageYOffset/document.doc umentElement. scrollTop/document. body. scrollTop in different browsers
Example:
Copy codeThe Code is as follows:
Window. scroll (0,100)
Console. log ("window. pageYOffset:" + window. pageYOffset)
Console.log(registrdocument.doc umentElement. scrollTop: registry.document.doc umentElement. scrollTop)
Console. log ("document. body. scrollTop:" + document. body. scrollTop)

IE6/7/8:
Doctype:
Window. pageYOffset: undefined
Document.doc umentElement. scrollTop: 100
Document. body. scrollTop: 0

No doctype:
Window. pageYOffset: undefined
Document.doc umentElement. scrollTop: 0
Document. body. scrollTop: 100
Safari/Chrome:
Window. pageYOffset: 100
Document.doc umentElement. scrollTop: 0
Document. body. scrollTop: 100

Firefox/Opera:

Doctype:
Window. pageYOffset: 100
Document.doc umentElement. scrollTop: 100
Document. body. scrollTop: 0

No doctype:
Window. pageYOffset: 100
Document.doc umentElement. scrollTop: 0
Document. body. scrollTop: 100

2. Obtain the scrollTop Value
Perfect short for getting scrollTop assignments:
Copy codeThe Code is as follows:
Var scrollTop = window. pageYOffset | document.doc umentElement. scrollTop | document. body. scrollTop;