Document.body.scrollTop value of 0 is a common solution to standard problems _javascript skills

When you do a page, you may use a fixed layer, read Document.body.scrollTop to set the position of the layer, like this:

Window.onscroll = function () {
var ofix = document.getElementById ("Divfix");
OFix.style.top = Document.body.scrollTop + "px";
}

But how did not achieve the expected effect, the output of the value of Document.body.scrollTop a look, has always been 0. It turned out to be a DTD problem, and if the page were to go straight to the beginning, there would be no problem. But to conform to the Web standards, the DTD is certainly not less. Use Document.documentElement.scrollTop instead of DOCUMENT.BODY.SCROLLTOP when you have a DTD. ­

Window.onscroll = function () {
var ofix = document.getElementById ("Divfix");
OFix.style.top = Document.documentElement.scrollTop + "px";
}

Editor's note:

When a page has a DTD (or DOCTYPE specified), use Document.documentelement.
When a page does not have a DTD (or no DOCTYPE specified), use Document.body.
This is true in both IE and Firefox.
For compatibility, you can use the following code: var scrolltop = Window.pageyoffset
|| Document.documentElement.scrollTop
|| Document.body.scrollTop
|| 0;