Why are websites getting mouse position in screen coordinates in the first place?
replies(8):
As for why they're checking for coordinates instead of checking for event.type is beyond me. Still I appreciate the write up, it is a good puzzle and relatable to come across code you didn't write and ask, why is it important that the click coordinate is nonzero? Why can't we just check that event.target is the button we want to activate? Why are we using JavaScript at all when a details/summary tag would do the same job?
Why would you just send a document when you can generate a heat map of where the user is on your website. And then complain about the performance and wonder why it costs so much to run a modern website.
Has anyone seen good use-cases for that feature? I'm thinking about dual window applications that interacts with each other (I think I saw a demo of something like this a while ago on HN but I wasn't able to find it again), or sites where behavior depends on their location on the virtual screen.
layerX[1] while non-standard is supported and returns a position relative to the top of the page or the top of the parent element. This makes coordinates positive only and 50,50 is the same for all users. For screenX, 3000,1567 is the same coordinate as 15,37 depending on where the window is located.
[1] https://developer.mozilla.org/en-US/docs/Web/API/MouseEvent/...
For example:
I'm with you on the second point - as unlikely as it is for the click to occur at the origin, it's still a legitimate value being abused as an indicator of something that might not actually be true - quite frankly the code was bad to begin with, and it was still bad after the fix.