To detect if the window meets a specific media query we use the
window.matchMedia('(max-width: 800px)').addListener( () => alert("Media query status changed!") );
The listener method will be called whenever the window will go below / under 800px. Below is a full working codepen.
More detail about the matchMedia here.
I may be wrong, but from what I've seen this can only be applied to the overall window container. So far there is no support for container media queries. Would have been nice to be able to write something like:
const myContainer = document.querySelector(".my-container"); myContainer.matchMedia('(max-width: 800px)').addListener( () => alert("Container media query status changed!") );