Simplifying code

JavaScript
1

I have come across the following code which I suspect is over-complicated in order to support legacy browsers. I imagine it can be simplified for modern browsers but I’m not sure how. I understand the ternary operator, but not the double one used here.

var thisTop =
  (el.style.top || el.style.pixelTop || el.offsetTop || 0) -
  (window.pageXOffset
    ? window.pageYOffset
    : document.documentElement.scrollTop
    ? document.documentElement.scrollTop
    : document.body.scrollTop);

Can anyone help? Thanks

2

They’re listed in order of preference, so you can just use window.pageYOffset, which is good for everything beyond IE8.

1 Like
3

Thanks, Paul. And do I need all of
(el.style.top || el.style.pixelTop || el.offsetTop || 0)
?

4

Nope, you can just use:

var thisTop = window.pageYOffset;
1 Like
5

Thanks, but that doesn’t quite work. My full code is in this pen based on one by @PaulOB with JS by Fellgall

6

Oh wait - there’s a subtraction in there. I didn’t see that before.

You’ll be wanting:

var thisTop = el.offsetTop - window.pageYOffset;
2 Likes
7

Just the ticket - thanks!

8

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