To read the current breakpoint tier in JavaScript, employ this CSS:
:root {
  --current-breakpoint-tier: xs;
  
  @media (min-width: $screen-sm-min) {
    --current-breakpoint-tier: sm;
  }
  @media (min-width: $screen-md-min) {
    --current-breakpoint-tier: md;
  }
  @media (min-width: $screen-lg-min) {
    --current-breakpoint-tier: lg;
  }
  @media (min-width: $screen-xl-min) {
    --current-breakpoint-tier: xl;
  }
  @media (min-width: $screen-xxl-min) {
    --current-breakpoint-tier: xxl;
  }
}
Then use this JavaScript:
// globally
getComputedStyle(document.documentElement).getPropertyValue('--current-breakpoint-tier')
// or locally
getComputedStyle(someElement).getPropertyValue('--current-breakpoint-tier')
If you're using Bootstrap and Sass, you can even do this:
\:root
  @each $name, $min-width in $grid-breakpoints
    @media (min-width: $min-width)
      --current-breakpoint-tier: #{$name}
Hat tip to Arne.
Posted by Dominik Schöler to makandra dev (2023-01-10 15:19)