PostCSS Short Position lets define sides within the position property in CSS.

.header {
  position: fixed 0 1em *;
}
/* becomes */
.header {
  top: 0;
  right: 1em;
  left: 1em;
  position: fixed;
}

The position declaration can be extended with the 1-to-4 syntax to target top, right, bottom, and left. Sides can be omitted using the skip token.

Add PostCSS Short Position to your project:

npm install postcss-short-position --save-dev

Use PostCSS Short Position to process your CSS:

const postcssShortPosition = require('postcss-short-position');
postcssShortPosition.process(YOUR_CSS /*, processOptions, pluginOptions */);

Or use it as a PostCSS plugin:

const postcss = require('postcss');
const postcssShortPosition = require('postcss-short-position');
postcss([
  postcssShortPosition(/* pluginOptions */)
]).process(YOUR_CSS /*, processOptions */);

PostCSS Short Position runs in all Node environments, with special instructions for:

The prefix option defines a prefix required by properties being transformed. Wrapping dashes are automatically applied, so that x would transform -x-position.

postcssShortPosition({ prefix: 'x' });

.header {
  x-position: fixed 0 1em *;
}
/* becomes */
.header {
  top: 0;
  right: 1em;
  left: 1em;
  position: fixed;
}

The skip option defines the skip token used to ignore portions of the shorthand.

postcssShortPosition({ skip: '-' });

.header {
  position: fixed 0 1em -;
}
/* becomes */
.header {
  top: 0;
  right: 1em;
  left: 1em;
  position: fixed;
}