babel-plugin-short-css-vars

Babel plugin using short-css-vars to shorten the names of CSS variables in JavaScript code.

CSS variables are renamed with a unique hash that is consistent across processed files. This allows you to have common style files that reference variables with varying values defined in theme files.

Installation

$ npm install babel-plugin-short-css-vars --save-dev

Example

Input

const sheet = document.createElement('style');
sheet.innerHTML = `
:root { --long-variable-name-that-defines-a-particular-color: blue; }
`;
 
const div = document.createElement('div');
div.style.color = "var(--long-variable-name-that-defines-a-particular-color)";

Output

const sheet = document.createElement('style');
sheet.innerHTML = `
:root { --vf2dsn: blue; }
`;
 
const div = document.createElement('div');
div.style.color = "var(--vf2dsn)";

This plugin also works with JSX/React source.

Usage

{
  "plugins": [
    "babel-plugin-short-css-vars"
  ]
}

See the babel docs for more configuration details.

Options

This plugin supports all the utility options. Because these options will need to be a RegExp or function, the Babel config willl need to be a JavaScript configuration file.

formatter

See the utility for how the default formatting works. If you wish to use a different pattern, simply provide a different formatter function via options.

// babel.config.js
const fnv1a = require('fnv1a');
 
module.exports = {
  "plugins": [
    [
      "babel-plugin-short-css-vars",
      {
        formatter: name => fnv1a(name).toString(36)
      }
    ]
  ]
}

The name provided to the formatter is the variable name WITHOUT the '--' prefix. The return value should also be name-only. So my-custom-var rather than --my-custom-var.

ignore

If you need to avoid hashing certain variable names, you can ignore them with this option by either RegExp, function, or string (which will be turned into RegExp). This can be useful if you are referencing CSS Variables in an app, yet you do not have control over some of the declarations.

// babel.config.js
module.exports = {
  "plugins": [
    [
      "babel-plugin-short-css-vars",
      {
        ignore: /^third-party-theme/
      }
    ]
  ]
}

In another scenario, if you have several short variable names (for example --blue) you can use a function to ignore names by length.

postcss([shortCssVars({
  ignore: name => name.length <= 4
})])

The name provided to ignore is the variable name WITHOUT the '--' prefix. So blue rather than --blue.

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