sample.js

var client = new gherkin.Client('http://127.0.0.1:9000');
function queryAccount(email, cb) {
  return client.accountExists(email)
    .done(
      function (exists) {
        var status = exists ? "registered" : "unregistered";
        cb(null, { status: status });
      },
      function (error) {
        cb({ error: error.message });
      }
    )
}

function verificationStatus(email, password, cb) {
  client.password = password;

  var setup = client.email ?
                  client.rawPasswordLogin() :
                  client.accountExists(email).then(client.rawPasswordLogin.bind(client, null));

  return setup
    .then(client.emailStatus.bind(client, null))
    .done(
      function (emailStatus) {
        var status = emailStatus.verified ? "verified" : "unverified";
        cb(null, { status: status });
      },
      function (error) {
        cb({ error: error.message });
      }
    )
}

function signIn(email, password, cb) {
  client.password = password;

  var setup = client.email ?
                  client.rawPasswordLogin() :
                  client.accountExists(email).then(client.rawPasswordLogin.bind(client, null));

  return setup
    .done(
      function (result) {
        cb(null, { sessionToken: result.sessionToken });
      },
      function (error) {
        cb({ error: error.message });
      }
    )
}

function signUp(email, password, cb) {
  var token;
  return client.rawPasswordCreate()
    .then(client.rawPasswordLogin.bind(client))
    .then(
      function (result) {
        token = result.sessionToken;
      }
    )
    .then(client.emailStatus.bind(client))
    .done(
      function (emailStatus) {
        cb({ needsConfirmation: !emailStatus.verified, sessionToken: token });
      },
      function (error) {
        cb({ error: error.message });
      }
    )
}