A driver to query Fauna databases in browsers, Node.js, and other Javascript runtimes
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.
Server-side
Node.js - Current and active LTS versions:
Cloud providers
Browsers
Stable versions of:
API reference documentation for the driver is available at https://fauna.github.io/fauna-js/. The docs are generated using TypeDoc.
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>
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(${dog}) {
id,
ts,
name
}
`;
// Run the query
const response = await client.query(documentQuery);
console.log(response);
} catch (error) {
if (error instanceof FaunaError) {
console.log(error);
}
} finally {
// Clean up any remaining resources
client.close();
}
The fql function is your gateway to building safe, reuseable Fauna queries.
It allows you compose queries from sub-queries and variables native to your program. Variables passed in are treated as unexecutable values in Fauna's API - preventing security issues like injection attacks.
For example:
import { Client, fql } from "fauna";
const client = new Client();
// Variables can be used as arguments in an FQL query
const collectionName = "Pets";
// Build a reusable sub-query to determine if a collection exists
const collectionExists = (name) => fql`Collection.byName(${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: ${collectionName} })
"Collection created"
}
`;
// Run the query
const response = await client.query(upsertCollectionQuery);
console.log(response.data);
client.close();
This has several advantages:
fql to build a library of subqueries applicable to your domain - and combinable in whatever way you need`${interpoloated_argument}`) parts of the query.fql`copied from terminal...` and the query will work as is.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();
QueryValue responsesTo 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);
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 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
}
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);
}
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);
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();
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.
The maximum backoff in seconds to be observed between each retry. Default 20 seconds.
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.
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 });
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 });
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 sethttp2_session_idle_msto small values.
Warning Setting
http2_session_idle_msto small values can lead to a race condition where requests cannot be transmitted before the session is closed, yieldingERR_HTTP2_GOAWAY_SESSIONerrors.
The driver supports Event Feeds.
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.
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);
}
Exceptions can be raised at two different places:
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);
}
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.
The driver supports Event Streaming.
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);
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
},
);
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;
}
}
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.
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!
gh repo clone fauna/fauna-js if you use the GitHub CLIyarn installyarn test. This will start local fauna containers, verify they're up and run all tests.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.
Linting runs automatically on each commit.
If you wish to run on-demand run yarn lint.
Distributed under the MPL 2.0 License. See LICENSE for more information.
FAQs
A driver to query Fauna databases in browsers, Node.js, and other Javascript runtimes
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