postcss-em

PostCSS plugin to convert px in em. Based on sass-em.

Breaking change in 3.0: changed default function name to em-convert to match postcss-rem, as CSS now use rem() for calculating the remainder.

How it works

The plugin provides a em-convert() function which takes at least 2 parameters: the value (px, mixed) and the context (px). There can be multiple comma-separated values (eg. multiple box shadow), but the last parameter must be the context.

Example

Input

.demo {
  font-size: em-convert(24px, 16px); /* Simple */
  padding: em-convert(5px 10px, 24px); /* Multiple values */
  margin: em-convert(10px 0.5em, 24px); /* Existing em value */
  border-bottom: em-convert(1px solid black, 24px); /* Multiple mixed values */
  box-shadow: em-convert(
    0 0 2px #ccc,
    inset 0 0 5px #eee,
    24px
  ); /* Comma-separated values */
  text-shadow: em-convert(1px 1px, 24px) #eee, em-convert(-1px, 24px) 0 #eee; /* Alternate use */
}

Output

.demo {
  font-size: 1.5em; /* Simple */
  padding: 0.20833em 0.41666em; /* Multiple values */
  margin: 0.41666em 0.5em; /* Existing em value */
  border-bottom: 0.04166em solid black; /* Multiple mixed values */
  box-shadow: 0 0 0.08333em #ccc, inset 0 0 0.20833em #eee; /* Comma-separated values */
  text-shadow: 0.04166em 0.04166em #eee, -0.04166em 0 #eee; /* Alternate use */
}

Usage

Install with npm i postcss-em and use with PostCSS:

postcss([require("postcss-em")]);

Example with custom options:

postcss([ require('postcss-em')({
  precision: 6       // Default to 5
  name: 'convert-em' // Default to 'em-convert'
}) ])

See PostCSS docs for examples for your environment.