A PostCSS plugin and Javascript runtime combination, which allows you to write @container queries in your CSS the same way you would write @media queries.

npm install --save-dev @zeecoder/container-query

• Container.js - JS Runtime
• containerQuery.js - PostCSS Plugin
• initialiseAllContainers.js - helper function

The rest in build/ is not considered to be a part of the Public API, which means anything in it can change at any time. (Including minor / patch releases.)

• @container queries cannot be nested

• Works with all modern browsers and IE9+

• Lead with ## WHAT (image) followed by ## WHY
• list supported browsers
• BEM-inspiration: Block -> inside of which are elements (unique classnames!)
• @container queries must always be preceded by a @define-container
• All @containers following a @defined-container will be related to that
• @define-container declarations will be ignored inside @container declarations
• Example function to save all container configurations in separate JSON files in a dir
• Gulp example
  • PostCSS example
  • SASS example: works out of the box
  • Less -> separate pipeline
• Containers can have more than one instance of their elements
• The container units are relative to the container's "inner" height / width. (Without the borders.)
• Note possible circular issues
  • A container should not use container units for properties that would affect its width / height. These situations are not currently handled, so try to avoid them.
• To avoid circular deps, use overflow: hidden and avoid using container units on defined containers
• Use native CSS techniques to achieve your goal whenever possible (css grid, flexbox)

Here is a list of goals I started with, in case you're wondering about the tool's design:

• Should be thoroughly unit tested
• Use containers (as opposed to "element query"),
• Resemble @media queries so that it's familiar and easy to use,
• Uses PostCSS for preprocessing instead of a JS runtime parser,
• Modular, so it plays nicely with js bundlers and "Component-based" UI libraries (Webpack / Browserify / React etc.)
• Doesn't need to be valid CSS syntax (since it's based on PostCSS)
• Be easy enough to use, but a transpiling step in the frontend build process would be assumed
• Should work especially well with css component naming methodologies, like BEM or SUIT