hanko-frontend-sdk

This package utilizes the Hanko API to provide functionality that allows an easier UI integration. It is meant for use in browsers only.

• Installation
• Usage
• Options
• Session Events
• Session Management
  • Getting the User Object
  • Validating a Session
  • Getting the Session Token
  • Logging out a User
• Translation of Outgoing Emails
• Custom Session Claim Type Safety
• FlowAPI
  • Initializing a New Flow
  • Understanding the State Object
  • Action Availability
  • Accessing Action Inputs
  • Running an Action
  • Event Handlers
  • Controlling the AfterStateChanged Event
  • Auto-Steps
  • Error Handling
  • Caching Flow State
• Bugs
• Documentation
• License

Installation

# npm
npm install @teamhanko/hanko-frontend-sdk

# yarn
yarn add @teamhanko/hanko-frontend-sdk

# pnpm
pnpm install @teamhanko/hanko-frontend-sdk

Usage

Import as a module:

import { Hanko } from "@teamhanko/hanko-frontend-sdk"

const hanko = new Hanko("http://localhost:3000")

With a script tag via CDN:

<script src="https://cdn.jsdelivr.net/npm/@teamhanko/hanko-frontend-sdk/dist/sdk.umd.js"></script>

<script>
    const hanko = new hankoFrontendSdk.Hanko("http://localhost:3000")
    ...
</script>

Options

You can pass certain options, when creating a new Hanko instance:

const defaultOptions = {
  timeout: 13000,                                // The timeout (in ms) for the HTTP requests.
  cookieName: "hanko",                           // The cookie name under which the session token is set.
  localStorageKey: "hanko",                      // The prefix / name of the localStorage keys.
  sessionCheckInterval: 30000,                   // Interval (in ms) for session validity checks. Must be greater than 3000 (3s).
  sessionCheckChannelName: "hanko-session-check" // The broadcast channel name for inter-tab communication

};
const hanko = new Hanko("http://localhost:3000", defaultOptions);

Session Events

You can bind callback functions to different custom events. The callback function will be called when the event happens and an object will be passed in, containing event details. The event binding works as follows:

// Controls the optional `once` parameter. When set to `true` the callback function will be called only once.
const once = false;

const removeEventListener = hanko.onSessionCreated((eventDetail) => {
    // Your code...
}, once);

The following events are available:

• "hanko-session-created": Will be triggered after a session has been created and the user has completed possible additional steps (e.g. passkey registration or password recovery). It will also be triggered when the user logs in via another browser window. The event can be used to obtain the JWT claims.

hanko.onSessionCreated((sessionDetail) => {
  // A new JWT has been issued.
    console.info("Session created", sessionDetail.claims);
})

• "hanko-session-expired": Will be triggered when the session has expired, or when the session has been removed in another browser window, because the user has logged out, or deleted the account.

hanko.onSessionExpired(() => {
  // You can redirect the user to a login page or show the `<hanko-auth>` element, or to prompt the user to log in again.
  console.info("Session expired");
})

• "hanko-user-logged-out": Will be triggered, when the user actively logs out. In other browser windows, a "hanko-session-expired" event will be triggered at the same time.

hanko.onUserLoggedOut(() => {
  // You can redirect the user to a login page or show the `<hanko-auth>` element.
  console.info("User logged out");
})

• "hanko-user-deleted": Will be triggered when the user has deleted the account. In other browser windows, a "hanko-session-expired" event will be triggered at the same time.

hanko.onUserDeleted(() => {
  // You can redirect the user to a login page or show the `<hanko-auth>` element.
  console.info("User has been deleted");
})

Please Take a look into the docs for more details.

Session Management

The SDK provides methods to manage user sessions and retrieve user information.

Getting the User Object

Fetches the current user's profile information.

• Returns: A User object containing the user’s profile details. The object includes:
  • user_id: A unique string identifier for the user.
  • passkeys: An optional array of WebAuthn credentials (passkey-based authentication).
  • security_keys: An optional array of WebAuthn credentials (security key-based authentication).
  • mfa_config: An optional configuration object for multi-factor authentication settings.
  • emails: An optional array of email objects (e.g., { address: string, is_primary: boolean, is_verified: boolean }).
  • username: An optional username object (e.g., { id: string, username: string }).
  • created_at: A string timestamp (ISO 8601) of when the user was created.
  • updated_at: A string timestamp (ISO 8601) of when the user was last updated.
• Errors: UnauthorizedError (invalid or expired session), TechnicalError (server or network issues).

try {
    const user = await hanko.getUser();
    console.log("User profile:", user);
    // Example output:
    // {
    //   user_id: "123e4567-e89b-12d3-a456-426614174000",
    //   emails: [{ address: "[email protected]", is_primary: true, is_verified: true }],
    //   username: { id: "f2882293-3c39-451d-a7cb-4cf3375e0c66", username: "johndoe" },
    //   created_at: "2025-01-01T10:00:00Z",
    //   updated_at: "2025-04-01T12:00:00Z"
    // }
} catch (error) {
    console.error("Failed to fetch user profile:", error);
    // Handle UnauthorizedError or TechnicalError
}

Validating a Session

Checks the validity of the current session.

• Returns: A SessionCheckResponse object containing:
  • is_valid: A boolean indicating whether the session is valid.
  • claims: An optional object with session details, including:
    • subject: The user ID or session identifier.
    • session_id: The unique session identifier.
    • expiration: A string timestamp (ISO 8601) when the session expires.
    • email: An optional object with email details (e.g., { address: string, is_primary: boolean, is_verified: boolean }).
    • username: An optional string with the user’s username.
    • issued_at, audience, issuer: Optional metadata about the session token.
    • Custom claims (defined by the application).
• Errors: TechnicalError (server or network issues).

try {
    const sessionStatus = await hanko.validateSession();
    console.log("Session status:", sessionStatus);
    // Example output:
    // {
    //   is_valid: true,
    //   claims: {
    //     subject: "123e4567-e89b-12d3-a456-426614174000",
    //     session_id: "789abc",
    //     expiration: "2025-04-25T12:00:00Z",
    //     email: { address: "[email protected]", is_primary: true, is_verified: true },
    //     custom_field: "value"
    //   }
    // }
} catch (error) {
    console.error("Failed to validate session:", error);
    // Handle TechnicalError
}

Getting the Session Token

Retrieves the current session token from the authentication cookie.

• Returns: A string containing the JWT session token or null if no session exists.
• Note: This method does not throw errors; check for null to handle missing sessions.

const token = hanko.getSessionToken();
console.log("Session token:", token);
// Example output: "eyJhbGciOiJIUzI1NiIs..."

Logging out a User

Logs out the current user by invalidating the session.

• Returns: A promise that resolves with no value on successful logout or throws an error.
• Errors: TechnicalError (server or network issues).
• Note: If no session exists, the method resolves without error.

try {
    await hanko.logout();
    console.log("User logged out");
} catch (error) {
    console.error("Failed to fetch user logout:", error);
    // Handle TechnicalError
}

Translation of outgoing emails

If you use the main Hanko client provided by the Frontend SDK, you can use the lang parameter in the options when instantiating the client to configure the language that is used to convey to the Hanko API the language to use for outgoing emails. If you have disabled email delivery through Hanko and configured a webhook for the email.send event, the value for the lang parameter is reflected in the JWT payload of the token contained in the webhook request in the "Language" claim.

Custom session claim type safety

The Hanko backend allows you to define custom claims that are added to issued session JWTs (see here for more info).

To allow for IDE autocompletion and to maintain type safety for your custom claims:

1. Create a TypeScript definition file (*.d.ts) in your project (alternatively, modify an existing one).
2. Import the Claims type from the frontend SDK.
3. Declare a custom type that extends the Claims type.
4. Add your custom claims to your custom type.

import type { Claims } from "@teamhanko/hanko-frontend-sdk" // 2.
// import type { Claims } from "@teamhanko/elements"        // alternatively, if you use Hanko Elements, which
                                                            // re-exports most SDK types


type CustomClaims = Claims<{                                // 3.
    custom_claim?: string                                   // 4.
}>;

5. Use your custom type when accessing claims, e.g. in session details received in event callbacks or when accessing claims in responses from session validation endpoints:

import type { CustomClaims } from "..."; // path to your type declaration file

hanko.onSessionCreated((sessionDetail) => {
  const claims = sessionDetail.claims as CustomClaims;
  console.info("My custom claim:", claims.custom_claim);
});

import type { CustomClaims } from "..."; // path to your type declaration file

async function session() {
    const session = await hanko.validateSession();
    const claims = session.claims as CustomClaims;
    console.info("My custom claim:", claims.custom_claim);
};

FlowAPI

The SDK offers a TypeScript-based interface for managing authentication and profile flows with Hanko, enabling the development of custom frontends with the Hanko FlowAPI. It handles state transitions, action execution, input validation, and event dispatching, while also providing built-in support for auto-stepping and passkey autofill. This guide explores its core functionality and usage patterns.

Initializing a New Flow

Start a new authentication or profile flow using the createState method on a Hanko instance. Options allow you to control event dispatching and auto-step behavior.

const state = await hanko.createState("login", {
    dispatchAfterStateChangeEvent: true,
    excludeAutoSteps: [],
    loadFromCache: true,
    cacheKey: "hanko-flow-state",
});

Parameters

• flowName: The name of the flow (e.g., "login", "register" or "profile").
• options:
  • dispatchAfterStateChangeEvent: boolean - Whether to dispatch the onAfterStateChange event after state changes (default: true).
  • excludeAutoSteps: AutoStepExclusion - Array of state names or "all" to skip specific or all auto-steps (default: null).
  • loadFromCache: boolean - Whether to attempt loading a cached state from localStorage (default: true).
  • cacheKey: string - The key used for localStorage caching (default: "hanko-flow-state").

Understanding the State Object

The state object represents the current step in the flow. It contains properties and methods to interact with the flow.

Structure

• name: StateName - The current state’s name (e.g., "login_init", "login_password", "success").
• flowName: FlowName - The name of the flow (e.g., "login").
• error: Error | undefined - An error object if an action or request fails (e.g., invalid input, network error).
• payload: Payloads[StateName] | undefined - State-specific data returned by the API.
• actions: ActionMap<StateName> - An object mapping action names to Action instances.
• csrfToken: string - CSRF token for secure requests.
• status: number - HTTP status code of the last response.
• invokedAction: ActionInfo | undefined - Details of the last action run on this state, if any.
• previousAction: ActionInfo | undefined - Details of the action that led to this state, if any.
• isCached: boolean - Whether the state was loaded from localStorage.
• cacheKey: string - The key used for localStorage caching.
• excludeAutoSteps: AutoStepExclusion - An array of StateNames excluded from auto-stepping.

Action Availability

Actions can be enabled or disabled based on the backend configuration or the user's state and properties. You can check whether a specific action is enabled by accessing its enabled property:

if (state.actions.example_action.enabled) {
  await state.actions.example_action.run();
} else {
  console.log("Action is disabled");
}

Accessing Action Inputs

Each action in state.actions has an inputs property defining expected input fields.

console.log(state.actions.continue_with_login_identifier.inputs);
// Example output:
// {
//   username: {
//     required: true,
//     type: "string",
//     minLength: 3,
//     maxLength: 20,
//     description: "User’s login name"
//   }
// }

Running an Action

Actions transition the flow to a new state. Use the run method on an action, passing input values and optional configuration.

Basic Example with Type Narrowing

if (state.name === "login_init") {
  const newState = await state.actions.continue_with_login_identifier.run({
    username: "user1",
  });
  // Triggers `onBeforeStateChange` and `onAfterStateChange` events
  // `newState` is the next state in the flow (e.g., "login_password")
}

Additional Considerations

• Type Narrowing: Check state.name to ensure the action exists and inputs are valid for that state.
• Events: By default, run triggers onBeforeStateChange before the action and onAfterStateChange after the new state is loaded.
• Validation Errors: If the action fails due to invalid input (e.g., wrong format or length), newState.error will be set to "invalid_form_data", and specific errors will be attached to the related input fields (see "Error Handling" below).

Event Handlers

The SDK dispatches events via the Hanko instance to track state changes.

onBeforeStateChange

Fires before an action is executed, useful for showing loading states.

hanko.onBeforeStateChange(({ state }) => {
  console.log("Action loading:", state.invokedAction);
});

onAfterStateChange

Fires after a new state is loaded, ideal for rendering UI or handling state-specific logic.

hanko.onAfterStateChange(({ state }) => {
  console.log("Action load finished:", state.invokedAction);

  switch (state.name) {
    case "login_init":
      state.passkeyAutofillActivation(); // Special handler for passkey autofill; requires an <input> field on the page with `autocomplete="username webauthn"` (e.g., <input type="text" name="username" autocomplete="username webauthn" />) so the browser can suggest and autofill passkeys when the user interacts with it.
      break;
    case "login_password":
      // Render password input UI
      if (state.error) {
        console.log("Error:", state.error); // e.g., "invalid_form_data"
      }
      break;
    case "error":
      // Handle network errors or 5xx responses
      console.error("Flow error:", state.error);
      break;
  }
});

Controlling the AfterStateChanged Event

You can disable the automatic onAfterStateChange event and dispatch it manually after custom logic.

if (state.name === "login_init") {
  const newState = await state.actions.continue_with_login_identifier.run(
    { username: "user1" },
    { dispatchAfterStateChangeEvent: false }, // Disable automatic dispatch
  );
  // Only `onBeforeStateChange` is triggered here

  await doSomething(); // Your custom async logic
  newState.dispatchAfterStateChangeEvent(); // Manually trigger the event
}

Auto-Steps

Auto-steps automatically advance the flow for certain states, reducing manual intervention.

Supported States

• preflight
• login_passkey
• onboarding_verify_passkey_attestation
• webauthn_credential_verification
• thirdparty
• success
• account_deleted

Disabling Auto-Steps

Prevent auto-steps by specifying states in excludeAutoSteps:

const state = await hanko.createState("login", {
  excludeAutoSteps: ["success"], // Skip auto-step for "success"
});

Manual Auto-Step Execution

hanko.onAfterStateChange(({ state }) => {
  if (state.name === "success") {
    console.log("Flow completed");
    await state.autoStep();
  }
});

Error Handling

Input Errors

If an action fails due to invalid inputs:

if (state.name === "login_password" && state.error === "invalid_form_data") {
  const passwordError = state.actions.password_login.inputs.password.error;
  console.log("Password error:", passwordError);
}

Network/API Errors

For network issues or 5xx responses, the error state is entered with details in state.error.

if (state.name === "error") {
    console.error("Flow error:", state.error);
}

Caching Flow State

Persist and recover flow state using localStorage.

Saving State

Save the current flow state to localStorage using saveToLocalStorage().

state.saveToLocalStorage(); // Stores under `state.cacheKey` (default: "hanko-flow-state")

Please note that the localStorage entry will be removed automatically when an action is invoked on the saved state.

Loading State

Recover a cached state or start a new flow:

const state = await hanko.createState("login", {
    loadFromCache: true, // Attempts to load from `cacheKey`
    cacheKey: "hanko-flow-state",
});

Clearing State

Remove the cached state:

state.removeFromLocalStorage(); // Deletes from `state.cacheKey`

Advanced Serialization

For custom persistence:

import { State } from "@teamhanko/hanko-frontend-sdk";

const serialized = state.serialize(); // Returns a `SerializedState` object
// Store `serialized` in your storage system

// Later, deserialize it
const recoveredState = await State.deserialize(hanko, serialized, {
    cacheKey: "custom-key",
});

This allows integration with other storage mechanisms.

Bugs

Found a bug? Please report on our GitHub page.

Documentation

To see the latest documentation, please click here.

License

The hanko-frontend-sdk project is licensed under the MIT License.