A Simple Query Syntax for CSS Element Queries

The goal of QSS is to define a simple syntax for specifying element queries by adding a new ending part between a CSS selector list and the block of rules that help define the breakpoints when those rules are to apply.

Normally in CSS you have something like this:

selectorList { block }

We are going to add a new part for our query between the selector list and the block where we will store instructions for when the rule should apply.

selectorList <query> { block }

Because this exists as a new part between the selector list and the block of rules, if you have a list of selectors like h1, h2, h3, h4, h5, h6 {} you only need to add the query once after the selector list is complete, like h1, h2, h3, h4, h5, h6 <query> {} rather than h1 <query>, h2 <query>, h3 <query>, ….

This document describes two different formats for expressing element queries for individual CSS rules, one using an if-based structure, and another that uses the @ symbol to declare when it should apply.

• operator: if
• condition: width | height | characters | children | xscroll | yscroll
• comparator: < | below | under | <= | max | == | equals | >= | min | > | above | over
• breakpoint: <number>

div if width above 500 {}

input if characters under 1 {}

• operator: @
• comparator: < | below | under | <= | max | == | equals | >= | min | > | above | over
• breakpoint: <number>
• condition: width | height | characters | children | xscroll | yscroll

div @ above 500 width {}

input @ under 1 characters {}

In both phrase formats the whitespace between tokens is optional, this means that if you prefer to think about these as @above or @min you can express them that way. The following should all equivalent:

div if width >= 500 {}
div if width >=500 {}
div if width min 500 {}
div @min 500 width {}
div@min500width{}
div @ >=500 width {}

The queries parsed by QSS would be split into the following pieces:

• selector list
• rule block (or stylesheet?)
• comparator
• condition
• breakpoint

And these could also be used to construct Element Queries for other syntaxes like:

• EQCSS
• Selectory
• and using functions like the container query mixin

Essentially QSS acts as a syntax to abstract away writing these: Useful Tests for JS-powered Styling

This repository contains a working proof of concept of a plugin to parse and read QSS syntax. In order to use this plugin you just need to include QSS on the page where you want it to display:

<script src=qss.js></script>

Then you're able to add queries written in QSS syntax to your site using one of the following methods: a <style> tag, a <link> tag with type=text/qss set, or a <script> tag with a type of text/qss either inline or linked externally using a src="" attribute:

<style type="text/qss"></style>

<link type="text/qss" href=stylesheet.qss rel=stylesheet>

<script type="text/qss"></script>

<script type="text/qss" src=stylesheet.qss></script>

• Website: tomhodgins.github.io/qss/
• Element Query Demo: tests/element-queries.html
• Test: tests/
• QSS Playground