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Faking env() to Use it Now

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There is already an env() function in CSS, but it kinda came out of nowhere as an Apple thing for dealing with “The Notch” but it has made it’s way to be a draft spec. The point will be for UAs or authors to declare variables that cannot be changed. Global const for CSS, sorta.

That spec doesn’t seem to suggest how we’ll actually set those env() values just yet. If you want them now, the easiest way to fake them would be using regular ol’ CSS custom properties and simply not change them.

But if you want that env() syntax though, there is a PostCSS plugin for emulating it. The way the plugin handles them is through a JavaScript file that declares them.

postcssCustomProperties({
  importFrom: 'path/to/file.js' /* module.exports = {
    environmentVariables: {
      '--branding-padding': '20px',
      '--branding-small': '600px'
    }
  } */
});

Having them start life as JavaScript is interesting, as it means we could perhaps have a single place to set variables that are accessible both to JavaScript and CSS.

That’s what Harry Nicholls covers more in his article, “Why you should use CSS env()” like some gotchas when dealing with units and such. But if you really needed a single source for unchangeable variables in both CSS and JavaScript, then I’d say this is a good way to go — and could potentially be ripped out once support for env() formally arrives.

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