RunKit + npm: postcss-rtl

const postcssRtl = require("postcss-rtl"); const postcss = require('postcss'); const css = ` .default-border { border-width: 5px 10px 15px 20px; } .reset-borders { border-width: 0; } `; const processed = postcss([postcssRtl()]).process(css); const result = processed.css;