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Neo4j Driver for JavaScript

This is the lite version of the official Neo4j driver for JavaScript.

Resources to get you started:

What's New in 4.3

Including the Driver

In Node.js application

Stable channel:

npm install neo4j-driver-lite

Pre-release channel:

npm install neo4j-driver-lite@next

Please note that @next only points to pre-releases that are not suitable for production use. To get the latest stable release omit @next part altogether or use @latest instead.

var neo4j = require('neo4j-driver-lite')

Driver instance should be closed when Node.js application exits:

driver.close() // returns a Promise

otherwise the application shutdown might hang or exit with a non-zero exit code.

In web browser

We build a special browser version of the driver, which supports connecting to Neo4j over WebSockets. It can be included in an HTML page using one of the following tags:

<!-- Direct reference -->
<script src="lib/browser/neo4j-lite-web.min.js"></script>

<!-- unpkg CDN non-minified -->
<script src="https://unpkg.com/neo4j-driver-lite"></script>
<!-- unpkg CDN minified for production use, version X.Y.Z -->
<script src="https://unpkg.com/neo4j-driver-lite@X.Y.Z/lib/browser/neo4j-lite-web.min.js"></script>

<!-- jsDelivr CDN non-minified -->
<script src="https://cdn.jsdelivr.net/npm/neo4j-driver-lite"></script>
<!-- jsDelivr CDN minified for production use, version X.Y.Z -->
<script src="https://cdn.jsdelivr.net/npm/neo4j-driver-lite@X.Y.Z/lib/browser/neo4j-lite-web.min.js"></script>

This will make a global neo4j object available, where you can create a driver instance with neo4j.driver:

var driver = neo4j.driver(
  'neo4j://localhost',
  neo4j.auth.basic('neo4j', 'password')
)

It is not required to explicitly close the driver on a web page. Web browser should gracefully close all open WebSockets when the page is unloaded. However, driver instance should be explicitly closed when it's lifetime is not the same as the lifetime of the web page:

driver.close() // returns a Promise

Usage examples

Constructing a Driver

// Create a driver instance, for the user `neo4j` with password `password`.
// It should be enough to have a single driver per database per application.
var driver = neo4j.driver(
  'neo4j://localhost',
  neo4j.auth.basic('neo4j', 'password')
)

// Close the driver when application exits.
// This closes all used network connections.
await driver.close()

Acquiring a Session

Regular Session

// Create a session to run Cypher statements in.
// Note: Always make sure to close sessions when you are done using them!
var session = driver.session()
with a Default Access Mode of READ
var session = driver.session({ defaultAccessMode: neo4j.session.READ })
with Bookmarks
var session = driver.session({
  bookmarks: [bookmark1FromPreviousSession, bookmark2FromPreviousSession]
})
against a Database
var session = driver.session({
  database: 'foo',
  defaultAccessMode: neo4j.session.WRITE
})

Executing Queries

Consuming Records with Streaming API

// Run a Cypher statement, reading the result in a streaming manner as records arrive:
session
  .run('MERGE (alice:Person {name : $nameParam}) RETURN alice.name AS name', {
    nameParam: 'Alice'
  })
  .subscribe({
    onKeys: keys => {
      console.log(keys)
    },
    onNext: record => {
      console.log(record.get('name'))
    },
    onCompleted: () => {
      session.close() // returns a Promise
    },
    onError: error => {
      console.log(error)
    }
  })

Subscriber API allows following combinations of onKeys, onNext, onCompleted and onError callback invocations:

Consuming Records with Promise API

// the Promise way, where the complete result is collected before we act on it:
session
  .run('MERGE (james:Person {name : $nameParam}) RETURN james.name AS name', {
    nameParam: 'James'
  })
  .then(result => {
    result.records.forEach(record => {
      console.log(record.get('name'))
    })
  })
  .catch(error => {
    console.log(error)
  })
  .then(() => session.close())

Transaction functions

// Transaction functions provide a convenient API with minimal boilerplate and
// retries on network fluctuations and transient errors. Maximum retry time is
// configured on the driver level and is 30 seconds by default:
// Applies both to standard and reactive sessions.
neo4j.driver('neo4j://localhost', neo4j.auth.basic('neo4j', 'password'), {
  maxTransactionRetryTime: 30000
})

Reading with Async Session

// It is possible to execute read transactions that will benefit from automatic
// retries on both single instance ('bolt' URI scheme) and Causal Cluster
// ('neo4j' URI scheme) and will get automatic load balancing in cluster deployments
var readTxResultPromise = session.readTransaction(txc => {
  // used transaction will be committed automatically, no need for explicit commit/rollback

  var result = txc.run('MATCH (person:Person) RETURN person.name AS name')
  // at this point it is possible to either return the result or process it and return the
  // result of processing it is also possible to run more statements in the same transaction
  return result
})

// returned Promise can be later consumed like this:
readTxResultPromise
  .then(result => {
    console.log(result.records)
  })
  .catch(error => {
    console.log(error)
  })
  .then(() => session.close())

Writing with Async Session

// It is possible to execute write transactions that will benefit from automatic retries
// on both single instance ('bolt' URI scheme) and Causal Cluster ('neo4j' URI scheme)
var writeTxResultPromise = session.writeTransaction(async txc => {
  // used transaction will be committed automatically, no need for explicit commit/rollback

  var result = await txc.run(
    "MERGE (alice:Person {name : 'Alice'}) RETURN alice.name AS name"
  )
  // at this point it is possible to either return the result or process it and return the
  // result of processing it is also possible to run more statements in the same transaction
  return result.records.map(record => record.get('name'))
})

// returned Promise can be later consumed like this:
writeTxResultPromise
  .then(namesArray => {
    console.log(namesArray)
  })
  .catch(error => {
    console.log(error)
  })
  .then(() => session.close())

Explicit Transactions

With Async Session

// run statement in a transaction
const txc = session.beginTransaction()
try {
  const result1 = await txc.run(
    'MERGE (bob:Person {name: $nameParam}) RETURN bob.name AS name',
    {
      nameParam: 'Bob'
    }
  )
  result1.records.forEach(r => console.log(r.get('name')))
  console.log('First query completed')

  const result2 = await txc.run(
    'MERGE (adam:Person {name: $nameParam}) RETURN adam.name AS name',
    {
      nameParam: 'Adam'
    }
  )
  result2.records.forEach(r => console.log(r.get('name')))
  console.log('Second query completed')

  await txc.commit()
  console.log('committed')
} catch (error) {
  console.log(error)
  await txc.rollback()
  console.log('rolled back')
} finally {
  await session.close()
}

Numbers and the Integer type

The Neo4j type system uses 64-bit signed integer values. The range of values is between -(2<sup>64</sup>- 1) and (2<sup>63</sup>- 1).

However, JavaScript can only safely represent integers between Number.MIN_SAFE_INTEGER -(2<sup>53</sup>- 1) and Number.MAX_SAFE_INTEGER (2<sup>53</sup>- 1).

In order to support the full Neo4j type system, the driver will not automatically convert to javascript integers. Any time the driver receives an integer value from Neo4j, it will be represented with an internal integer type by the driver.

Any javascript number value passed as a parameter will be recognized as Float type.

Writing integers

Numbers written directly e.g. session.run("CREATE (n:Node {age: $age})", {age: 22}) will be of type Float in Neo4j.

To write the age as an integer the neo4j.int method should be used:

var neo4j = require('neo4j-driver-lite')

session.run('CREATE (n {age: $myIntParam})', { myIntParam: neo4j.int(22) })

To write an integer value that are not within the range of Number.MIN_SAFE_INTEGER -(2<sup>53</sup>- 1) and Number.MAX_SAFE_INTEGER (2<sup>53</sup>- 1), use a string argument to neo4j.int:

session.run('CREATE (n {age: $myIntParam})', {
  myIntParam: neo4j.int('9223372036854775807')
})

Reading integers

In Neo4j, the type Integer can be larger what can be represented safely as an integer with JavaScript Number.

It is only safe to convert to a JavaScript Number if you know that the number will be in the range Number.MIN_SAFE_INTEGER -(2<sup>53</sup>- 1) and Number.MAX_SAFE_INTEGER (2<sup>53</sup>- 1).

In order to facilitate working with integers the driver include neo4j.isInt, neo4j.integer.inSafeRange, neo4j.integer.toNumber, and neo4j.integer.toString.

var smallInteger = neo4j.int(123)
if (neo4j.integer.inSafeRange(smallInteger)) {
  var aNumber = smallInteger.toNumber()
}

If you will be handling integers that is not within the JavaScript safe range of integers, you should convert the value to a string:

var largeInteger = neo4j.int('9223372036854775807')
if (!neo4j.integer.inSafeRange(largeInteger)) {
  var integerAsString = largeInteger.toString()
}

Enabling native numbers

Starting from 1.6 version of the driver it is possible to configure it to only return native numbers instead of custom Integer objects. The configuration option affects all integers returned by the driver. Enabling this option can result in a loss of precision and incorrect numeric values being returned if the database contains integer numbers outside of the range [Number.MIN_SAFE_INTEGER, Number.MAX_SAFE_INTEGER]. To enable potentially lossy integer values use the driver's configuration object:

var driver = neo4j.driver(
  'neo4j://localhost',
  neo4j.auth.basic('neo4j', 'password'),
  { disableLosslessIntegers: true }
)

Building

./buildDependencies.sh
npm install
npm run build
npn rub build:browser

This produces browser-compatible standalone files under lib/browser and a Node.js module version under lib/. See files under ../examples/ on how to use.

Testing

Tests require latest Testkit 4.3, Python3 and Docker.

Testkit is needed to be cloned and configured to run against the Javascript Lite Driver. Use the following steps to configure Testkit.

  1. Clone the Testkit repository
git clone https://github.com/neo4j-drivers/testkit.git
  1. Under the Testkit folder, install the requirements.
pip3 install -r requirements.txt
  1. Define some enviroment variables to configure Testkit
export TEST_DRIVER_NAME=javascript
export TEST_DRIVER_REPO=<path for the root folder of driver repository>
export TEST_DRIVER_LITE=1

To run test against against some Neo4j version:

python3 main.py

More details about how to use Teskit could be found on its repository

Simple npm test can also be used if you want to run only the unit tests.

For development, you can have the build tool rerun the tests each time you change the source code:

npm run test:watch

The guides about how to test the driver internal dependencies should be found on it own Readme files.

See ../core and ../bolt-connection