Mongo c# driver ObjectId to Guid converter nodejs

converter.js

const b64ToGuid = (b64) => {
  const bytes = Buffer.from(b64, "base64");

  bits = [];
  bytes.forEach(byte => {
    bits.push(byte.toString(16).padStart(2, '0'));
  });
  const data = bits.join("");
  const parts = [];
  parts.push(data.substring(0, 8).split("").reverse().join(""));
  parts.push(data.substring(8, 12).split("").reverse().join(""));
  parts.push(data.substring(12, 16).split("").reverse().join(""));
  parts.push(data.substring(16, 20));
  parts.push(data.substring(20));

  return parts.join("-");
}

const guidToB64 = (guid) => {
  const data = guid.replaceAll("-", "");
  const parts = [];
  parts.push(data.substring(0, 8).split("").reverse().join(""));
  parts.push(data.substring(8, 12).split("").reverse().join(""));
  parts.push(data.substring(12, 16).split("").reverse().join(""));
  parts.push(data.substring(16, 20));
  parts.push(data.substring(20));

  const bytes = [];
  parts.join("").match(/.{1,2}/g).forEach(bit => {
    bytes.push(parseInt(bit, 16));
  });

  const buff = Buffer.from(bytes);
  return buff.toString("base64");
}

const b = "MyIRAFVEd2aImaq7zN3u/w==";
const g = b64ToGuid(b);
const b64 = guidToB64(g);
console.log(g); 
console.log(b64);