How to decode/encode string to base64 in typescript express server

in Node typescript:

import { Buffer } from "buffer";

const b64 = "SGVsbG8sIFdvcmxkIQ==";
const str="Hello, World!"

const decode = (str: string):string => Buffer.from(str, 'base64').toString('binary');
const encode = (str: string):string => Buffer.from(str, 'binary').toString('base64');

test('base64 decode', () => {
  expect(decode(b64)).toEqual(str)
});

test('base64 decode', () => {
  expect(encode(str)).toEqual(b64)
});

test('base64 encode/decode', () => {
  expect(decode(encode(str))).toEqual(str)
});