Question

Normally when getting the offset using jQuery I do offset().left. My understanding is that offsetLeft is pure javascript, so why not use this over the jQuery offset().left? Does it really help anything cross-browser? or?

And when using offset().left i’ve seen people take out the () so it’s just offset.left, is this okay to do? Is it only okay to do if there’s nothing in the parenthesis?

As a side note: I’ve heard that in IE7 when using the jQuery way of offset().top it gives a screwey offset based on how much you’ve scrolled. Someone in the comments on the jQuery API page for offset() said document.getElementById(anchor).offsetTop fixed it.

Answer 1

Getting offsets can be a little tricky in some browsers. offsetTop and -Left are incorrect in IE 6 and below and others like offsetX and offsetY are completely inconsistent across browsers (see Quirksmode)

Generally, when a library includes some functionality even when the same functionality seems to already exist, it’s usually done for cross-browser purposes.

As far as I can tell, using offset.left instead of offset().left shouldn’t even work. The latter would be “get the left property of the object returned by the offset() function”, which is what you’d want. The former, with no parentheses, would be “get the left property of the function offset“, which doesn’t make much sense to me (unless the object whose offset property you’re accessing isn’t a jQuery wrapper, in which case the offset property might not be a function, but instead an object with left and top properties).

But I’m not a jQuery expert