Code pulled from https://github.com/StarbaseAlpha/Cryptic to give encryption example (without library)

example.js

async function Example() {

  const encode = (byteArray) => {
    return btoa(Array.from(new Uint8Array(byteArray)).map(val => {
      return String.fromCharCode(val);
    }).join('')).replace(/\+/g, '-').replace(/\//g, '_').replace(/\=/g, '');
  };

  const createECDH = async (curve = "P-256") => {
    let DH = await crypto.subtle.generateKey({
      "name": "ECDH",
      "namedCurve": curve
    }, true, ['deriveBits']);
    let pub = await crypto.subtle.exportKey('spki', DH.publicKey);
    let key = await crypto.subtle.exportKey('pkcs8', DH.privateKey);
    return {
      "pub": encode(pub),
      "key": encode(key)
    };
  };

  const decode = (str) => {
    return new Uint8Array(atob(str.replace(/\_/g, '/').replace(/\-/g, '+')).split('').map(val => {
      return val.charCodeAt(0);
    }));
  };


  const fromText = (string) => {
    return new TextEncoder().encode(string);
  };


  const random = (size) => {
    return crypto.getRandomValues(new Uint8Array(size));
  };


  const pbkdf2 = async (bits, salt, iterations = 1, size = 256, hashAlg = "SHA-256") => {

    let key = await crypto.subtle.importKey('raw', bits, {
      "name": "PBKDF2"
    }, false, ['deriveBits']);

    let result = await crypto.subtle.deriveBits({
      "name": "PBKDF2",
      "salt": salt,
      "iterations": iterations,
      "hash": hashAlg
    }, key, size);

    return encode(result);

  };


  const encrypt = async (plaintext, bits, AD = null) => {
    let key = await crypto.subtle.importKey('raw', bits, {
      "name": "AES-GCM"
    }, false, ['encrypt']);
    let iv = random(12);
    let msg = fromText(plaintext);
    let cipher = await crypto.subtle.encrypt({
      "name": "AES-GCM",
      "iv": iv,
      "additionalData": AD || fromText('')
    }, key, msg);
    return encode(iv) + '.' + encode(cipher);
  };

  const passwordEncrypt = async (message, password = "", iterations = 100000) => {
    let salt = random(32);
    let keyBits = await pbkdf2(fromText(password), salt, iterations, 256);
    let encrypted = await encrypt(message, decode(keyBits));
    return encode(fromText(iterations.toString())) + '.' + encode(salt) + '.' + encrypted;
  };


  let keys = await createECDH()
  let sealed = await passwordEncrypt(keys.key, "password", 100000);
  console.log(keys);
  console.log(sealed);

}