When to Use
- Writing JS/TS code that connects to Neo4j (Node.js or browser)
- Setting up driver, sessions, transactions, or query execution
- Debugging Integer handling, result consumption, session leaks, async errors
- TypeScript type annotations for driver objects
When NOT to Use
- Writing/optimizing Cypher →
neo4j-cypher-skill
- Upgrading driver version →
neo4j-migration-skill
- RxJS session API → references/rxjs-session.md
Install
npm install neo4j-driver # or: yarn add neo4j-driver
Environment Variables
Load connection config from environment — never hardcode credentials.
# .env file (add to .gitignore)
NEO4J_URI=neo4j+s://xxx.databases.neo4j.io
NEO4J_USERNAME=neo4j
NEO4J_PASSWORD=secret
NEO4J_DATABASE=neo4j
// npm install dotenv (for Node.js < 20 or when .env auto-load is off)
import 'dotenv/config' // or: require('dotenv').config()
const URI = process.env.NEO4J_URI
const USER = process.env.NEO4J_USERNAME
const PASSWORD = process.env.NEO4J_PASSWORD
const DATABASE = process.env.NEO4J_DATABASE ?? 'neo4j'
Node 20+ natively loads .env with --env-file .env. Next.js / Vite auto-load .env — no dotenv import needed.
Driver Lifecycle
Create one driver instance at startup. Share everywhere. Never create per-request.
// CommonJS
const neo4j = require('neo4j-driver')
// ESM / TypeScript
import neo4j from 'neo4j-driver'
const driver = neo4j.driver(
process.env.NEO4J_URI, // 'neo4j+s://xxx.databases.neo4j.io'
neo4j.auth.basic(process.env.NEO4J_USER, process.env.NEO4J_PASSWORD)
)
await driver.verifyConnectivity() // fail fast on startup if unreachable
// On shutdown:
await driver.close()
URI schemes:
| Scheme | Transport | Use |
|---|
neo4j+s:// | TLS + cluster routing | Aura; production clusters |
neo4j:// | plaintext + cluster routing | local dev cluster |
bolt+s:// | TLS, single instance | single Neo4j instance with TLS |
bolt:// | plaintext, single instance | local single instance |
Auth options:
neo4j.auth.basic(user, password) // username/password
neo4j.auth.bearer(token) // SSO / JWT
neo4j.auth.kerberos(base64Ticket) // Kerberos
neo4j.auth.none() // unauthenticated (dev only)
Singleton for web frameworks — create once, import everywhere:
// db.js
let _driver = null
export function getDriver() {
if (!_driver) _driver = neo4j.driver(process.env.NEO4J_URI,
neo4j.auth.basic(process.env.NEO4J_USER, process.env.NEO4J_PASSWORD))
return _driver
}
export async function closeDriver() {
if (_driver) { await _driver.close(); _driver = null }
}
Serverless (Lambda/Vercel/Workers): keep maxConnectionPoolSize: 5; no guaranteed SIGTERM.
Choose the Right API
| API | Use when | Auto-retry | Result |
|---|
driver.executeQuery() | Default for most queries | ✅ | eager (all records) |
session.executeRead/Write() | Large results, streaming, multi-query tx | ✅ | lazy stream |
session.run() | LOAD CSV, CALL IN TRANSACTIONS, scripts | ❌ | lazy stream |
executeQuery — Default
const { records, summary, keys } = await driver.executeQuery(
'MATCH (p:Person {name: $name})-[:KNOWS]->(f) RETURN f.name AS name',
{ name: 'Alice' },
{ database: 'neo4j', routing: neo4j.routing.READ }
)
for (const record of records) {
console.log(record.get('name')) // use .get() — records are NOT plain objects
}
// Write and count results
const { summary: s } = await driver.executeQuery(
'CREATE (p:Person {name: $name, age: $age})',
{ name: 'Bob', age: neo4j.int(30) },
{ database: 'neo4j' }
)
console.log(s.counters.updates().nodesCreated) // ✅ must call .updates()
Always specify database — omitting causes an extra round-trip.
❌ Never template-literal Cypher:
// ❌ injection risk + disables plan caching
await driver.executeQuery(`MATCH (p:Person {name: '${name}'}) RETURN p`)
// ✅ parameterised
await driver.executeQuery('MATCH (p:Person {name: $name}) RETURN p', { name })
Managed Transactions (executeRead / executeWrite)
Auto-retried on transient failures. Consume records inside the callback — the stream is gone when the callback returns.
const session = driver.session({ database: 'neo4j' })
try {
const names = await session.executeRead(async tx => {
const result = await tx.run(
'MATCH (p:Person) WHERE p.name STARTS WITH $prefix RETURN p.name AS name',
{ prefix: 'Al' }
)
// ✅ collect() while tx is open; return plain data
return (await result.collect()).map(r => r.get('name'))
})
await session.executeWrite(async tx => {
await tx.run('MERGE (p:Person {name: $name})', { name: 'Carol' })
})
} finally {
await session.close() // always in finally
}
Critical: await tx.run() returns a stream handle, not records.
// ❌ returns stream; tx closes; records = []
return await tx.run('MATCH (p:Person) RETURN p.name AS name')
// ✅ collect fully inside callback
const result = await tx.run('MATCH (p:Person) RETURN p.name AS name')
return (await result.collect()).map(r => r.get('name'))
// ✅ or stream with for-await
for await (const record of result) { names.push(record.get('name')) }
Callback may execute more than once (retry on transient failure) — no side effects inside:
// ❌ fetch() called on every retry
await session.executeWrite(async tx => {
await fetch('https://api.example.com/notify')
await tx.run('CREATE ...')
})
// ✅ side effects after confirmed commit
await session.executeWrite(async tx => { await tx.run('MERGE ...') })
await fetch('https://api.example.com/notify')
session.run — Implicit Transactions
Not auto-retried. Use for LOAD CSV / CALL IN TRANSACTIONS / scripting only.
const session = driver.session({ database: 'neo4j' })
try {
const result = await session.run('CREATE (p:Person {name: $name}) RETURN p', { name: 'Alice' })
console.log(result.summary.counters.updates().nodesCreated)
} finally {
await session.close()
}
Session Close — Always in finally
// ❌ session leaks if executeRead rejects
session.executeRead(async tx => { ... })
.then(result => doSomething(result))
.then(() => session.close())
// ✅ guaranteed close
try {
const result = await session.executeRead(async tx => { ... })
doSomething(result)
} finally {
await session.close()
}
// ✅ promise-chain equivalent
session.executeRead(async tx => { ... })
.then(doSomething)
.catch(handleError)
.finally(() => session.close())
Integer Handling
Neo4j integers are 64-bit; JS Number is IEEE 754 (safe up to 2^53−1). Driver returns custom Integer by default.
Three modes:
// Mode 1 (default): Integer class — safe for all values, requires conversion
const driver1 = neo4j.driver(URI, auth)
// record.get('count') → Integer { low: 42, high: 0 }
// Mode 2: native JS number — only safe within Number.MAX_SAFE_INTEGER
const driver2 = neo4j.driver(URI, auth, { disableLosslessIntegers: true })
// record.get('count') → 42
// Mode 3: BigInt — precise but breaks JSON.stringify
const driver3 = neo4j.driver(URI, auth, { useBigInt: true })
// record.get('count') → 42n
Working with Integer class:
const count = record.get('count') // Integer { low: 42, high: 0 }
neo4j.isInt(count) // true
neo4j.integer.inSafeRange(count) // check before toNumber()
count.toNumber() // 42 (only safe within MAX_SAFE_INTEGER)
count.toString() // '42' (always safe)
count.toBigInt() // 42n
// Send integer parameter — plain JS number sends as FLOAT
await driver.executeQuery('CREATE (p:Person {age: $age})', { age: neo4j.int(30) })
JSON serialization pitfalls:
// ❌ Integer → {"low":42,"high":0}
JSON.stringify({ age: record.get('age') })
// ❌ BigInt → TypeError: Do not know how to serialize a BigInt
// ✅ convert first
JSON.stringify({ age: record.get('age').toNumber() })
// ✅ or use disableLosslessIntegers: true
// ❌ temporal types → {} silently
JSON.stringify({ dt: record.get('created') })
// ✅
JSON.stringify({ dt: record.get('created').toString() })
Record Access
Records are not plain objects — use .get():
const record = records[0]
record.get('name') // ✅ by key
record.get(0) // ✅ by index
record.keys // ['name', 'age']
record.has('name') // true
record.name // ❌ undefined
record['name'] // ❌ undefined
record.toObject() returns plain JS keys but values are still driver types (Integers, temporals). Not JSON-safe without conversion.
Error Handling
import { Neo4jError, SERVICE_UNAVAILABLE, SESSION_EXPIRED } from 'neo4j-driver'
try {
await driver.executeQuery('...', {}, { database: 'neo4j' })
} catch (err) {
if (err instanceof Neo4jError) {
if (err.code === 'Neo.ClientError.Schema.ConstraintValidationFailed') { /* unique constraint */ }
if (err.code === SERVICE_UNAVAILABLE) { /* unreachable */ }
if (err.code === SESSION_EXPIRED) { /* open a new session */ }
if (err.retriable) { /* transient — executeQuery already retried to exhaustion */ }
}
}
executeQuery and executeRead/Write auto-retry retriable errors. session.run does not.
TypeScript
import neo4j, { Driver, Session, ManagedTransaction, Record, Node, Integer } from 'neo4j-driver'
const driver: Driver = neo4j.driver(URI, neo4j.auth.basic(USER, PASSWORD))
const session: Session = driver.session({ database: 'neo4j' })
const names: string[] = await session.executeRead(
async (tx: ManagedTransaction): Promise<string[]> => {
const result = await tx.run('MATCH (p:Person) RETURN p.name AS name')
return (await result.collect()).map((r: Record) => r.get('name') as string)
}
)
// Typed node — Integer generic changes with disableLosslessIntegers
const node = record.get('p') as Node<Integer>
const age: number = node.properties.age.toNumber()
// With disableLosslessIntegers: true → Node<number>; age is already number
Batch Writes with UNWIND
// ❌ one transaction per item
for (const p of people) { await driver.executeQuery('CREATE ...', p) }
// ✅ single transaction
await driver.executeQuery(
`UNWIND $people AS person
MERGE (p:Person {name: person.name})
SET p.age = person.age`,
{ people }, // array of plain objects; numeric fields must be JS numbers, not neo4j.int()
{ database: 'neo4j' }
)
Common Mistakes
| Mistake | Fix |
|---|
| Template literal Cypher | Use $param placeholders |
record.name / record['name'] | record.get('name') |
JSON.stringify on Integer | .toNumber() or disableLosslessIntegers |
JSON.stringify on temporal | .toString() first |
summary.counters.nodesCreated | summary.counters.updates().nodesCreated |
Omit database | Always { database: 'neo4j' } |
Return result from tx callback | Return await result.collect() or mapped data |
.then(() => session.close()) | try/finally { await session.close() } |
| Side effects inside tx callback | Move outside — callback may retry |
| New driver per request | Create once at startup |
bolt:// or neo4j:// in browser | Use neo4j+s:// (WSS) |
| Integer in UNWIND array | Convert to plain JS Number first |
maxConnectionPoolSize: 100 in serverless | Use 5–10 per function instance |
References
Load on demand:
- references/data-types.md — full type mapping table, temporal types, graph types (Node/Relationship/Path), spatial types (Point/WGS-84/Cartesian),
neo4j.UUID [6.2+], toNative() conversion helper
- references/advanced-patterns.md — explicit transactions, causal consistency/bookmarks, connection pool tuning, result transformers, lazy streaming, repository pattern
- references/browser-usage.md — WebSocket URIs, CORS, bundler config, security guidance
- references/rxjs-session.md — RxJS session API (
rxSession.run(), observable patterns)
Checklist