rem を 10/16 倍する

adjust-rem.js

#!/usr/bin/env node

/**
 * @fileoverview rem を 10/16 倍する
 * @example cat styles.css | ./adjust-rem > styles.css
 */

const { readFileSync } - require("fs");
const postcss = require("postcss");

const plugin = postcss.plugin("adjust-rem", () => {
  return (root) => {
    root.replaceValues(/([-.\d])+rem/g, { fast: "rem" }, (string) => {
      const value = parseFloat(string.replace(/^\./, "0."));
      return (value * 10) / 16 + "rem";
    });
  };
});

const input = readFileSync(process.stdin.fd, { encoding: "utf-8" })
postcss([plugin])
  .process(input)
  .then((result) => console.log(result.toString()));