[Postman] pre-request scripts – auth token

const postRequest = {
  url: pm.environment.get("LOGIN_URL"),
  method: 'POST',
  header: { "Content-Type": "application/json" },
  body: {
    mode: 'application/json',
    raw: JSON.stringify({ 
          username: pm.environment.get("USER_LOGIN"),
          password: pm.environment.get("USER_PASSWORD") 
    })}
};
pm.sendRequest(postRequest, function (err, res) {
    var responseJson = res.json();
    console.log(responseJson);
    pm.environment.set('TOKEN', responseJson['token']);
});