JavaScript RFC7636 PKCE code_verifier and SHA-256 code_challenge with Web Cryptography API

pkce.js

//https://tools.ietf.org/html/rfc7636#appendix-B

const code_verifier = btoa(
  String.fromCharCode(...crypto.getRandomValues(new Uint8Array(32)))
).replace(/\/|\+|=/g, (x) => ({ "/": "_", "+": "-", "=": "" }[x]));

const hash = await crypto.subtle.digest(
  "SHA-256",
  new Uint8Array([...code_verifier].map((e) => e.charCodeAt(0)))
);

const code_challenge = btoa(
  String.fromCharCode(...new Uint8Array(hash))
).replace(/\/|\+|=/g, (x) => ({ "/": "_", "+": "-", "=": "" }[x]));