Neo4j Lite Driver for JavaScript

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

This version of the driver has the same capabilities as the Neo4j Driver except for the support of reactive sessions.
This means it doesn't have the RxJS dependency and the Driver#rxSession api.

Starting with 5.0, the Neo4j Drivers will be moving to a monthly release cadence. A minor version will be released on the last Friday of each month so as to maintain versioning consistency with the core product (Neo4j DBMS) which has also moved to a monthly cadence.

As a policy, patch versions will not be released except on rare occasions. Bug fixes and updates will go into the latest minor version and users should upgrade to that. Driver upgrades within a major version will never contain breaking API changes.

See also: https://neo4j.com/developer/kb/neo4j-supported-versions/

Resources to get you started:

- API Documentation
- Neo4j Driver Manual
- Neo4j Cypher Cheatsheet

What's New in 5.x

- Changelog

Including the Driver

$3

Stable channel:

``shell
npm install neo4j-driver-lite
`

Pre-release channel:

`shell
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.

In Common JS modules:

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

In ECMA Script modules:

`javascript
import neo4j from 'neo4j-driver-lite'
`

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

`javascript
driver.close() // returns a Promise
`

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

$3

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:

`html







`

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

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

From 5.4.0, this version is also exported as ECMA Script Module.
It can be imported from a module using the following statements:

`javascript
// Direct reference
import neo4j from 'lib/browser/neo4j-lite-web.esm.min.js'

// unpkg CDN non-minified , version X.Y.Z where X.Y.Z >= 5.4.0
import neo4j from 'https://unpkg.com/neo4j-driver-lite@X.Y.Z/lib/browser/neo4j-lite-web.esm.js'

// unpkg CDN minified for production use, version X.Y.Z where X.Y.Z >= 5.4.0
import neo4j from 'https://unpkg.com/neo4j-driver-lite@X.Y.Z/lib/browser/neo4j-lite-web.esm.min.js'

// jsDelivr CDN non-minified, version X.Y.Z where X.Y.Z >= 5.4.0
import neo4j from 'https://cdn.jsdelivr.net/npm/neo4j-driver-lite@X.Y.Z/lib/browser/neo4j-lite-web.esm.js'

// jsDelivr CDN minified for production use, version X.Y.Z where X.Y.Z >= 5.4.0
import neo4j from 'https://cdn.jsdelivr.net/npm/neo4j-driver-lite@X.Y.Z/lib/browser/neo4j-lite-web.esm.min.js'

`

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:

`javascript
driver.close() // returns a Promise
`

Usage examples

$3

`javascript
// 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()
`

$3

#### Regular Session

`javascript
// 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

`javascript
var session = driver.session({ defaultAccessMode: neo4j.session.READ })
`

##### with Bookmarks

`javascript
var session = driver.session({
bookmarks: [bookmark1FromPreviousSession, bookmark2FromPreviousSession]
})
`

##### against a Database

`javascript
var session = driver.session({
database: 'foo',
defaultAccessMode: neo4j.session.WRITE
})
`

$3

#### Consuming Records with Streaming API

`javascript
// 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:

- zero or one onKeys,
- zero or more onNext followed by onCompleted when operation was successful. onError will not be invoked in this case
- zero or more onNext followed by onError when operation failed. Callback onError might be invoked after couple onNext invocations because records are streamed lazily by the database. onCompleted will not be invoked in this case.

#### Consuming Records with Promise API

`javascript
// 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())
`

$3

`javascript
// 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

`javascript
// 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

`javascript
// 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())
`

$3

#### With Async Session

`javascript
// 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()
}
`

$3

The Neo4j type system uses 64-bit signed integer values. The range of values is between -(264- 1) and (263- 1).

However, JavaScript can only safely represent integers between Number.MIN_SAFE_INTEGER -(253- 1) and Number.MAX_SAFE_INTEGER (253- 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:

`javascript
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 -(253- 1) and Number.MAX_SAFE_INTEGER (253- 1), use a string argument to neo4j.int:

`javascript
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 -(253- 1) and Number.MAX_SAFE_INTEGER (253- 1).

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

`javascript
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:

`javascript
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:

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