CODEWITHSUNDEEP
javascriptdom
Ben G
Ben G

Reputation: 26771

Does JavaScript wait for this DOM event to finish?

Suppose I modify the HTML DOM on line 1. Can I be sure that line 2 of the JavaScript will be working with the DOM modifications enacted by line 1?

This is the only explanation I can come up with some buggy behavior I've been having on a form. The previous line is supposed to update the DOM, but sometimes the DOM is not updates by the time it's not on the next one. Things seem to work fine when I go slower though.

Upvotes: 0

Views: 686

Answers (2)

selbie
selbie

Reputation: 104514

Updating a specific property on a DOM element happens right away and should persist on a subsequent read of that property.

If you are relying on that change to propagate across the the DOM, it can be tricky. For example, such as changing the size of an element and expecting the sibling element to report a new offset position as a result - the latter may may not happen until the stack unwinds. I don't actually know the exact rules, but you have to be careful - and it is sometimes browser dependent behavior. And scary yet, sometimes throwing an alert to help debug this makes the elements "realize" their new layout right away. Then you take the alert out and it goes back to buggy behavior.

So if you are positive that a DOM change hasn't had the impact right away, then sometimes the thing to do is to call "setTimeout" with a callback function and a time value of 0. When the timer callback completes, you can complete the subsequent processing. YMMV

Upvotes: 1

Michael Berkowski
Michael Berkowski

Reputation: 270607

Yes, the Javascript DOM modifications will occur sequentially, unless you are waiting for an asynchronous AJAX call to return. The next instruction will not occur until the first has completed. However please show your code!

Upvotes: 1

Related Questions