Function for Decoding JWT Tokens to Access JWT Payload via JavaScript (No Library)

jwtDecoder.js

// Decodes a JWT with JavaScript
function jwtDecoder(token) {
  // 1. Split and Target the Payload Portion of the JWT Token String
  // 2. atob() to Decode the JWT's Base64 Encoded String into Readable JSON String
  // 3. Convert JSON String to parsable JSON Object
  return JSON.parse(atob(token.split('.')[1]));
}