Official JavaScript Driver for Fauna v10 (current)

This driver can only be used with FQL v10, and is not compatible with earlier versions of FQL. To query your databases with earlier API versions, see the faunadb package.

See the Fauna Documentation for additional information on how to configure and query your databases.

Supported runtimes

Server-side

Node.js - Current and active LTS versions:

• Current - v22
• LTS - v20
• LTS (Maintenance) - v18

Cloud providers

• Cloudflare Workers
• AWS Lambda
• Netlify
• Vercel

Browsers

Stable versions of:

• Chrome 69+
• Firefox 62+
• Safari 12.1+
• Edge 79+

API reference

API reference documentation for the driver is available at https://fauna.github.io/fauna-js/. The docs are generated using TypeDoc.

Install

The driver is available on npm. You can install it using your preferred package manager. For example:

npm install fauna

Browsers can import the driver using a CDN link:

<script type="module">
  import * as fauna from "https://cdn.jsdelivr.net/npm/fauna@latest/dist/browser/index.js";
</script>

Usage

By default, the driver's Client instance authenticates with Fauna using an access token in the FAUNA_SECRET environment variable. If needed, you can pass the token to the client using the secret argument instead.

import { Client, fql, FaunaError } from "fauna";
// Use `require` for CommonJS:
// const { Client, fql, FaunaError } = require('fauna');

const client = new Client();
// To configure your client:
// const client = new Client({
//   secret: YOUR_FAUNA_SECRET,
// });

try {
  // Build a query using the `fql` method
  const collectionQuery = fql`Collection.create({ name: "Dogs" })`;
  // Run the query
  const collectionResponse = await client.query(collectionQuery);

  // Declare a var for app data
  const dog = { name: "Scout" };

  // Build a query using the var
  const documentQuery = fql`
    Dogs.create(${dog}) {
      id,
      ts,
      name
    }
  `;

  // Run the query
  const response = await client.query(documentQuery);
  console.log(response);
} catch (error) {
  if (error instanceof FaunaError) {
    console.log(error);
  }
} finally {
  // Clean up any remaining resources
  client.close();
}

Write FQL queries

The fql function is your gateway to building safe, reuseable Fauna queries.

It allows you compose queries from sub-queries and variables native to your program. Variables passed in are treated as unexecutable values in Fauna's API - preventing security issues like injection attacks.

For example:

import { Client, fql } from "fauna";

const client = new Client();

// Variables can be used as arguments in an FQL query
const collectionName = "Pets";

// Build a reusable sub-query to determine if a collection exists
const collectionExists = (name) => fql`Collection.byName(${name}) != null`;

// Build query that uses the previous var and sub-query
const upsertCollectionQuery = fql`
  if (${collectionExists(collectionName)}) {
    "Collection already exists"
  } else {
    Collection.create({ name: ${collectionName} })
    "Collection created"
  }
`;

// Run the query
const response = await client.query(upsertCollectionQuery);
console.log(response.data);

client.close();

This has several advantages:

• You can use fql to build a library of subqueries applicable to your domain - and combinable in whatever way you need
• Injection attacks are not possible if you pass input variables into the interpolated (`${interpoloated_argument}`) parts of the query.
• The driver speaks "pure" FQL - you can try out some FQL queries on the dashboard's terminal and paste it directly into your app like fql`copied from terminal...` and the query will work as is.

Typescript support

With TypeScript, you can apply a type parameter to your result.

import { fql, Client, type QuerySuccess } from "fauna";

const client = new Client();

type User = {
  name: string;
  email: string;
};

const query = fql`{
  name: "Alice",
  email: "alice@site.example",
}`;

const response: QuerySuccess<User> = await client.query<User>(query);
const userDoc: User = response.data;

console.assert(userDoc.name === "Alice");
console.assert(userDoc.email === "alice@site.example");

client.close();

Alternatively, you can apply a type parameter directly to your fql statements and Client methods will infer your return types. Due to backwards compatibility, if a type parameter is provided to Client methods, it will override the inferred type from your query.

const query = fql<User>`{
  name: "Alice",
  email: "alice@site.example",
}`;

// response will be typed as QuerySuccess<User>
const response = await client.query(query);

// userDoc will be automatically inferred as User
const userDoc = response.data;

console.assert(userDoc.name === "Alice");
console.assert(userDoc.email === "alice@site.example");

client.close();

Interfaces as QueryValue responses

To use a custom interface as a query response, extend the QueryValueObject interface.

interface User extends QueryValueObject {
  name: string;
  email: string;
}

const query = fql`{
  name: "Alice",
  email: "alice@site.example",
}`;

const response: QuerySuccess<User> = await client.query<User>(query);

Query options

Options are available to configure queries on each request. These override any default query options in the client configuration.

import { fql, Client, type QueryOptions } from "fauna";

const client = new Client();

const options: QueryOptions = {
  arguments: { name: "Alice" },
  format: "tagged",
  long_type: "number",
  linearized: false,
  max_contention_retries: 5,
  query_tags: { name: "readme_query" },
  query_timeout_ms: 60_000,
  traceparent: "00-750efa5fb6a131eb2cf4db39f28366cb-000000000000000b-00",
  typecheck: true,
};

const response = await client.query(fql`"Hello, #{name}!"`, options);
console.log(response.data);

client.close();

Query statistics

Query statistics are returned with successful query responses and errors of the ServiceError type.

import {
  fql,
  Client,
  ServiceError,
  type QueryInfo,
  type QueryStats,
  type QuerySuccess,
} from "fauna";

const client = new Client();

try {
  const response: QuerySuccess<string> = await client.query<string>(
    fql`"Hello world"`,
  );
  const stats: QueryStats | undefined = response.stats;
  console.log(stats);
} catch (error: any) {
  if (error instanceof ServiceError) {
    const info: QueryInfo = error.queryInfo;
    const stats: QueryStats | undefined = info.stats;
  }
}

Example output:

{
  compute_ops: 1,
  read_ops: 0,
  write_ops: 0,
  query_time_ms: 15,
  storage_bytes_read: 0,
  storage_bytes_write: 0,
  contention_retries: 0
}

Pagination

Use paginate() to iterate sets that contain more than one page of results.

paginate() accepts the same query options as query().

import { fql, Client, type SetIterator, type QueryValue } from "fauna";

const client = new Client();

// Adjust `pageSize()` size as needed.
const query = fql`
  Product
    .byName("limes")
    .pageSize(60) { description }`;

const options = {
  query_timeout_ms: 60_000,
};

const pages: SetIterator<QueryValue> = client.paginate(query, options);

for await (const products of pages) {
  for (const product of products) {
    console.log(product);
  }
}

client.close();

Use flatten() to get paginated results as a single, flat array:

const pages: SetIterator<QueryValue> = client.paginate(query, options);

for await (const product of pages.flatten()) {
  console.log(product);
}

Client configuration

The driver's Client instance comes with reasonable defaults that should be used in most cases. You can override these defaults if needed.

In addition to configuring the client, you can also set default query options.

import { Client, endpoints, type ClientConfiguration } from "fauna";

const config: ClientConfiguration = {
  // Configure the client
  client_timeout_buffer_ms: 5000,
  endpoint: endpoints.default,
  fetch_keepalive: false,
  http2_max_streams: 100,
  http2_session_idle_ms: 5000,
  secret: YOUR_FAUNA_SECRET,

  // Set default query options
  format: "tagged",
  long_type: "number",
  linearized: false,
  max_attempts: 3,
  max_backoff: 20,
  max_contention_retries: 5,
  query_tags: { name: "readme_query" },
  query_timeout_ms: 60_000,
  traceparent: "00-750efa5fb6a131eb2cf4db39f28366cb-000000000000000b-00",
  typecheck: true,
};

const client = new Client(config);

Environment variables

The driver will default to configuring your client with the values of the FAUNA_SECRET and FAUNA_ENDPOINT environment variable.

For example, if you set the following environment variables:

export FAUNA_SECRET=YOUR_FAUNA_SECRET
export FAUNA_ENDPOINT=https://db.fauna.com/

You can initalize the client with a default configuration:

const client = new Client();

Retry

Max attempts

The maximum number of times a query will be attempted if a retryable exception is thrown (ThrottlingError). Default 3, inclusive of the initial call. The retry strategy implemented is a simple exponential backoff.

To disable retries, pass max_attempts less than or equal to 1.

Max backoff

The maximum backoff in seconds to be observed between each retry. Default 20 seconds.

Timeouts

There are a few different timeout settings that can be configured; each comes with a default setting. We recommend that most applications simply stick to the defaults.

Query timeout

The query timeout is the time, in milliseconds, that Fauna will spend executing your query before aborting with a 503 Timeout error. If a query timeout occurs, the driver will throw an instance of QueryTimeoutError.

The query timeout can be set using the query_timeout_ms client configuration option. The default value if you do not provide one is 5000 ms (5 seconds).

const client = new Client({ query_timeout_ms: 20_000 });

The query timeout can also be set to a different value for each query using the query_timeout_ms query option. Doing so overrides the client configuration when performing this query.

const response = await client.query(myQuery, { query_timeout_ms: 20_000 });

Client timeout

The client timeout is the time, in milliseconds, that the client will wait for a network response before canceling the request. If a client timeout occurs, the driver will throw an instance of NetworkError.

The client timeout is always the query timeout plus an additional buffer. This ensures that the client always waits for at least as long Fauna could work on your query and account for network latency. The client timeout buffer is configured by setting the client_timeout_buffer_ms option. The default value for the buffer if you do not provide on is 5000 ms (5 seconds), therefore the default client timeout is 10000 ms (10 s) when considering the default query timeout.

const client = new Client({ client_timeout_buffer_ms: 6000 });

HTTP/2 session idle timeout

The HTTP/2 session idle timeout is the time, in milliseconds, that an HTTP/2 session will remain open after there is no more pending communication. Once the session idle time has elapsed the session is considered idle and the session is closed. Subsequent requests will create a new session; the session idle timeout does not result in an error.

Configure the HTTP/2 session idle timeout using the http2_session_idle_ms option. The default value if you do not provide one is 5000 ms (5 seconds).

This setting only applies to clients using HTTP/2 implementations; for example, the default client for Node.js runtimes.

const client = new Client({ http2_session_idle_ms: 6000 });

Note Your application process may continue executing after all requests are completed for the duration of the session idle timeout. To prevent this, it is recommended to call close() once all requests are complete. It is not recommended to set http2_session_idle_ms to small values.

Warning Setting http2_session_idle_ms to small values can lead to a race condition where requests cannot be transmitted before the session is closed, yielding ERR_HTTP2_GOAWAY_SESSION errors.

Event Feeds

The driver supports Event Feeds.

Request an Event Feed

An Event Feed asynchronously polls an event source for events.

To get an event source, append eventSource() or eventsOn() to a supported Set.

To get paginated events, pass the event source to feed():

const response = await client.query(fql`
  let set = Product.all()

  {
    initialPage: set.pageSize(10),
    eventSource: set.eventSource()
  }
`);
const { initialPage, eventSource } = response.data;

const feed = client.feed(eventSource);

If changes occur between the creation of the event source and the feed() request, the feed replays and emits any related events.

You can also pass a query that produces an event source directly to feed():

const query = fql`Product.all().eventsOn(.price, .stock)`;

const feed = client.feed(query);

If you pass an event source query to feed(), the driver creates the event source and requests the event feed at the same time.

Iterate on an Event Feed

feed() returns a FeedClient instance that can act as an AsyncIterator. You can use for await...of to iterate through all the pages:

const query = fql`Product.all().eventsOn(.price, .stock)`;
const feed = client.feed(query);

for await (const page of feed) {
  console.log("Page stats", page.stats);

  for (event in page.events) {
    switch (event.type) {
      case "update":
      case "add":
      case "remove":
        console.log("Event: ", event);
        // ...
        break;
    }
  }
}

Alternatively, use flatten() to get paginated results as a single, flat array:

const query = fql`Product.all().eventsOn(.price, .stock)`;
const feed = client.feed(query);

for await (const event of feed.flatten()) {
  console.log("Event: ", event);
}

Error handling

Exceptions can be raised at two different places:

1. While fetching a page
2. While iterating a page's events

This distinction allows for you to ignore errors originating from event processing. For example:

const feed = client.feed(fql`
  Product.all().map(.details.toUpperCase()).eventSource()
`);

try {
  for await (const page of feed) {
    // Pages will stop at the first error encountered.
    // Therefore, its safe to handle an event failures
    // and then pull more pages.
    try {
      for (const event of page.events) {
        console.log("Event: ", event);
      }
    } catch (error: unknown) {
      console.log("Feed event error: ", error);
    }
  }
} catch (error: unknown) {
  console.log("Non-retryable error: ", error);
}

Event Feed options

The client configuration sets the default options for feed(). You can pass a FeedClientConfiguration object to override these defaults:

const options: FeedClientConfiguration = {
  long_type: "number",
  max_attempts: 5,
  max_backoff: 1000,
  query_timeout_ms: 5000,
  client_timeout_buffer_ms: 5000,
  secret: "FAUNA_SECRET",
  cursor: undefined,
  start_ts: undefined,
};

client.feed(fql`Product.all().eventSource()`, options);

You can reuse cursors across event sources with identical queries in the same database.

Event Streaming

The driver supports Event Streaming.

Start a stream

To get an event source, append eventSource() or eventsOn() to a set from a supported source.

To start and subscribe to the stream, pass the event source to stream():

const response = await client.query(fql`
  let set = Product.all()

  {
    initialPage: set.pageSize(10),
    eventSource: set.eventSource()
  }
`);
const { initialPage, eventSource } = response.data;

client.stream(eventSource);

You can also pass a query that produces an event source directly to stream():

const query = fql`Product.all().eventsOn(.price, .stock)`;

client.stream(query);

Iterate on a stream

You can iterate on the stream using an async loop:

try {
  for await (const event of stream) {
    switch (event.type) {
      case "update":
      case "add":
      case "remove":
        console.log("Event: ", event);
        // ...
        break;
    }
  }
} catch (error) {
  // An error will be handled here if Fauna returns a terminal, "error" event, or
  // if Fauna returns a non-200 response when trying to connect, or
  // if the max number of retries on network errors is reached.
  // ... handle fatal error
}

Or you can use a callback function:

stream.start(
  function onEvent(event) {
    switch (event.type) {
      case "update":
      case "add":
      case "remove":
        console.log("Event: ", event);
        // ...
        break;
    }
  },
  function onFatalError(error) {
    // An error will be handled here if Fauna returns a terminal, "error" event, or
    // if Fauna returns a non-200 response when trying to connect, or
    // if the max number of retries on network errors is reached.
    // ... handle fatal error
  },
);

Close a stream

Use close() to close a stream:

const stream = await client.stream(fql`Product.all().eventSource()`);

let count = 0;
for await (const event of stream) {
  console.log("Event: ", event);
  // ...
  count++;

  // Close the stream after 2 events
  if (count === 2) {
    stream.close();
    break;
  }
}

Stream options

The client configuration sets default options for the stream() method.

You can pass an StreamClientConfiguration object to override these defaults:

const options: StreamClientConfiguration = {
  long_type: "number",
  max_attempts: 5,
  max_backoff: 1000,
  secret: "YOUR_FAUNA_SECRET",
  status_events: true,
  cursor: null,
};

client.stream(fql`Product.all().eventSource()`, options);

For supported properties, see StreamClientConfiguration in the API reference.

Contributing

Any contributions from the community are greatly appreciated!

If you have a suggestion that would make this better, please fork the repo and create a pull request. You may also simply open an issue. We provide templates, so please complete those to the best of your ability.

Don't forget to give the project a star! Thanks again!

Set up the repo

1. Clone the repository; e.g. gh repo clone fauna/fauna-js if you use the GitHub CLI
2. Install dependencies via yarn install

Run tests

1. Start a docker desktop or other docker platform.
2. Run yarn test. This will start local fauna containers, verify they're up and run all tests.

Asserting types

In cases where you are modifying types and need to test type enforcement, you can use @ts-expect-error. Using @ts-expect-error will supress any type errors on the following line. Conversely, if there's no error, TypeScript will report its usage as not being neccessary.

To learn more about @ts-expect-error, you can read more about it in the TypeScript release notes.

Lint your code

Linting runs automatically on each commit.

If you wish to run on-demand run yarn lint.

License

Distributed under the MPL 2.0 License. See LICENSE for more information.