Solution to the document. body. scrollTop value is always 0

Use document.doc umentElement to specify doctype. During page creation, a fixed-position layer may be used to read document. body. scrollTop to set the layer position, as shown in the following figure:

Window. onscroll = function (){
Var oFix = document. getElementById ("pfix ");
OFix. style. top = document. body. scrollTop + "px ";
}

But why didn't it achieve the expected results? the output value of document. body. scrollTop is always 0. It turns out to be a problem with DTD. If the page starts with it, there will be no problem. However, to comply with the web standards, DTD is of course indispensable. Use document.doc umentElement. scrollTop to replace document. body. scrollTop with a DTD. ­

Window. onscroll = function (){
Var oFix = document. getElementById ("pfix ");
OFix. style. top = document.doc umentElement. scrollTop + "px ";
}

Editor's note:

When a page has a DTD (or DOCTYPE specified), use document.doc umentElement.
Document. body is used when a page does not have a DTD (or DOCTYPE is not specified.
This is true in both IE and Firefox.
For compatibility, you can use the following code: var scrollTop = window. pageYOffset
| Document.doc umentElement. scrollTop
| Document. body. scrollTop
| 0;