The best thing since sliced bread and absolutely the most revolutionary thing I have seen in my time as Dev, is CSS variables, it's shocking because it's something that should have been there from day one.
Let's get to the question, given I can get and set CSS variables in JavaScript π₯°, can I also watch for changes to the CSS values on the fly?
Other than polling, are there any ways to observe a live CSS variable change?
onCustomPropertyChange
I think the answer is no.
Top comments (10)
Maybe you could use a MutationObserver?
But it would depend highly on what you are doing. Watching the value is not trivial and depends on many factors. Take into account that CSS variables can change their value in many different ways and within many different scopes.
This would do the trick π₯°
Why should you do this?
Based on the reaction of this post
π© JavaScript Enhanced Scss mixins! π© concepts explained
Adam Crockett γ» Jul 26 '19 γ» 3 min read
Jess has become a language, you can see in my series jesslang, and part of the compiled code would ideally watch for changes so that CSS can become reactive in a narrow scope.
There would be a fair bit to read in my posts so forget the why, how?
If you are curious still, here is the first of jess-lang
10000 followers π₯³π₯ project preview: Jess language design.
Adam Crockett γ» Dec 21 '19 γ» 2 min read
Look into using MutationObserver with CSSOM: codepen.io/tainan/pen/vvzbwv
Also worth checking out cssobj/cssobj and zeit/styled-jsx to see how a few other projects handle reactive css aspects with javascript.
also worth looking into what can be done with houdini. π©π
Reactive css is tricky, css variables are tricky, when they are evaluated, how and where they are set, in what ways and when they are static or dynamic, the cascade of full/partial inheritance/override both to and from, late unsetting, invalid value handling and falling back, the interplay of different units, etc. there are some helpful tricks like calc() wraps etc. this is all new exciting ground for css! π
best of luck, it is exciting seeing these concepts being explored and pushed forward! π
How about vuejs.org/v2/guide/computed.html#C...?
Vue is reactive and will also help you extend any features you might need in the future and has watchers for events.
Indeed the reactive idea is what I am looking for and Vue is the inspiration for what I am talking about, but this is a bit high level, I'm looking for probably MutationObserver
I can't think of a single use case. Do you have one?
After reading the comments above?