Refresh a JWT on Postman without having to input the token constantly on the header.

postman-pre-request-script.js

// Data location
const ENV_EMAIL = 'email';
const ENV_HOST = 'hostname';
const ENV_PASS = 'password';
const ENV_TOKEN = 'idToken';

/**
 * Determine if a token is expired already
 */
function isTokenExpired(idToken) {
  if(!idToken) return null;

  // Split token parts
  let encoded = idToken.split('.')[1];
  // Decode payload
  let data = atob(encoded);
  // Parse JSON
  let payload = JSON.parse(data);

  // Compare expiration date
  let expirationDate = new Date(payload.exp*1000);
  let now = new Date();

  return expirationDate <= now;
}

// Check whether there is a token on the environment and it is expired
if(pm.environment.has(ENV_TOKEN) && isTokenExpired(pm.environment.get(ENV_TOKEN))) {
  // Retrieve an auth token from the login endpoint
  if(
    pm.environment.has(ENV_EMAIL) && 
    pm.environment.has(ENV_PASS) && 
    pm.environment.has(ENV_HOST)
  ) {
    const authLoginRequest = {
      url: pm.environment.get(ENV_HOST)+'/auth/login',
      method: 'POST',
      header: [
        'accept:application/x.api.v2+json',
        'content-type:application/json', 
      ],
      body: {
        mode: 'raw',
          raw: JSON.stringify({ 
          email: pm.environment.get(ENV_EMAIL),
          password: pm.environment.get(ENV_PASS)
        })
      }
    };
      
    // Save the token on the environment for future requests
    pm.sendRequest(authLoginRequest, function(err, response) {
      let token = response.json().data.token;
      pm.environment.set(ENV_TOKEN, token);
    });
  }
}