RunKit + npm: postcss-rtl

var postcssRtl = require("postcss-rtl"); var postcss = require("postcss"); const css = ` /*rtl:begin:ignore*/ fieldset { border: 0; } .other { border: 1px; } /*rtl:end:ignore*/ .themo { border: 2px; } `; const result = postcss([postcssRtl()]).process(css); const final = result.css;