Node.js SDK - API Reference

Every public symbol exported by @westyx-nexus/sdk-nodejs. All read methods are synchronous (cache-backed); only create, evaluateFlags, evaluateAB, and close are async.

Construction

`NexusClient.create(config: NexusConfig): Promise<NexusClient>`

Creates a client and runs a blocking initial sync.

const client = await NexusClient.create({
  endpoint: '...',
  apiKey:   '...',
});

Throws	When
`NexusInitError`	The initial sync failed for any reason. The `cause` property carries the underlying error (often `NexusUnauthorizedError` or a transport-level error).

The SSE stream and the polling timer start automatically once the initial sync succeeds.

Configs

`client.getConfig(key: string): string | undefined`

Returns the resolved config value, or undefined if the key is absent.

const dbHost = client.getConfig('DB_HOST');

public-key clients only see configs where is_public: true.

`client.getAllConfigs(): Record<string, string>`

Snapshot copy of every config key-value pair currently in the cache.

Feature flags

`client.getFlag(key: string, defaultValue?: boolean): boolean`

Returns the is_active state of a flag, or defaultValue (default false) when the key is absent.

client.getFlag('checkout.v2');           // false if missing
client.getFlag('checkout.v2', true);     // true if missing

`client.getAllFlags(): Record<string, boolean>`

Snapshot copy of every flag key-is_active pair in the cache.

`client.evaluateFlags(keys: string[]): Promise<Record<string, boolean>>`

Live network call to the server’s batch evaluator. Useful when you need the most recent state and don’t want to wait for the next sync.

const result = await client.evaluateFlags(['flag-a', 'flag-b']);
// => { 'flag-a': true, 'flag-b': false }

Missing keys resolve to false - never throws for an unknown key.

`client.evaluateAB(keys, userId, attributes?): Promise<Record<string, boolean>>`

Per-user AB evaluation (requires the AB Testing add-on on your project).

await client.evaluateAB(
  ['checkout-v2', 'dark-mode'],
  'user-abc123',
  { plan: 'pro', country: 'HU' },
);
// => { 'checkout-v2': true, 'dark-mode': false }

Throws NexusAbAddonNotAvailableError (HTTP 403) if the AB Testing add-on is not active on this project.

Secrets (secret key only)

`client.getSecret(key: string): string`

Returns the plaintext value of a text-type secret.

const password = client.getSecret('DB_PASSWORD');

Throws	When
`NexusPublicKeyError`	The client uses a public key
`NexusSecretNotFoundError`	The key is not in the cache, or it is a file-type secret (use `getSecretFilePath`)

`client.getSecretFilePath(key: string): string | undefined`

Returns the filesystem path of a file-type secret (PEM cert, JSON service account key, etc.), or undefined if the key does not exist or is a text-type secret.

const certPath = client.getSecretFilePath('TLS_CERT');
// /tmp/nexus-secrets/nexus-TLS_CERT-abc123def456

The SDK writes the secret content to a temp file on every sync when the value changes. Old temp files for the same key are deleted automatically. client.close() removes all temp files.

Throws	When
`NexusPublicKeyError`	The client uses a public key

Write API (secret key only)

The write API lets you create, update, and delete secrets programmatically. All three methods check the key type before making any network call - public keys throw NexusPublicKeyError immediately.

`client.setSecret(key: string, value: string): Promise<void>`

Creates or updates a secret (POST /v1/secrets, type: "text").

await client.setSecret('stripe.key', newKey);

Throws	When
`NexusPublicKeyError`	public key (no HTTP call)
`NexusUnauthorizedError`	HTTP 401
`NexusRateLimitedError`	HTTP 429

`client.deleteSecret(key: string): Promise<void>`

Deletes all versions of a secret (DELETE /v1/secrets/:key). Key is URL-encoded automatically.

await client.deleteSecret('old.api.key');

Throws	When
`NexusPublicKeyError`	public key (no HTTP call)
`NexusNotFoundError`	HTTP 404 - key doesn’t exist
`NexusRateLimitedError`	HTTP 429

`client.deleteSecretVersion(key: string, version: number): Promise<void>`

Deletes a specific version of a secret (DELETE /v1/secrets/:key?version=N).

await client.deleteSecretVersion('db.password', 2);

Throws	When
`NexusPublicKeyError`	public key (no HTTP call)
`NexusNotFoundError`	HTTP 404 - key or version doesn’t exist
`NexusRateLimitedError`	HTTP 429

Metadata

Property	Type	Description
`client.keyType`	`'sk' \| 'pk'`	Detected from the configured `apiKey`.
`client.syncedAt`	`Date \| null`	Timestamp of the last successful sync.
`client.streamStatus`	`'connected' \| 'fallback' \| 'disconnected'`	Current SSE state.

Sync / lifecycle

`client.connectStream()` / `client.disconnectStream()`

The stream starts automatically after the initial sync. Call disconnectStream() to opt out (e.g. on a “go offline” signal); call connectStream() to restart.

`client.close(): Promise<void>`

Stops the SSE connection, the polling timer, and removes all temp secret files. Always call on shutdown.

process.on('SIGTERM', async () => {
  await client.close();
  process.exit(0);
});

Error types

import {
  NexusError,                  // base class
  NexusInitError,              // initial sync failure (cause carries detail)
  NexusUnauthorizedError,      // HTTP 401
  NexusNotFoundError,          // HTTP 404
  NexusPublicKeyError,         // getSecret with public key
  NexusSecretNotFoundError,    // unknown secret key
  NexusRateLimitedError,       // HTTP 429 on write endpoints (v0.5.0)
  NexusQuarantinedError,       // HTTP 429 quarantine body (v0.4.0)
  NexusAbAddonNotAvailableError, // HTTP 403 on evaluateAB (v0.4.0)
} from '@westyx-nexus/sdk-nodejs';

See Error handling for full semantics and examples.

Overview

Backend SDKs

Browser SDKs

OpenFeature Providers

Node.js SDK - API Reference

Construction

`NexusClient.create(config: NexusConfig): Promise<NexusClient>`

Configs

`client.getConfig(key: string): string | undefined`

`client.getAllConfigs(): Record<string, string>`

Feature flags

`client.getFlag(key: string, defaultValue?: boolean): boolean`

`client.getAllFlags(): Record<string, boolean>`

`client.evaluateFlags(keys: string[]): Promise<Record<string, boolean>>`

`client.evaluateAB(keys, userId, attributes?): Promise<Record<string, boolean>>`

Secrets (secret key only)

`client.getSecret(key: string): string`

`client.getSecretFilePath(key: string): string | undefined`

Write API (secret key only)

`client.setSecret(key: string, value: string): Promise<void>`

`client.deleteSecret(key: string): Promise<void>`

`client.deleteSecretVersion(key: string, version: number): Promise<void>`

Metadata

Sync / lifecycle

`client.connectStream()` / `client.disconnectStream()`

`client.close(): Promise<void>`

Error types

​Construction

​NexusClient.create(config: NexusConfig): Promise<NexusClient>

​Configs

​client.getConfig(key: string): string | undefined

​client.getAllConfigs(): Record<string, string>

​Feature flags

​client.getFlag(key: string, defaultValue?: boolean): boolean

​client.getAllFlags(): Record<string, boolean>

​client.evaluateFlags(keys: string[]): Promise<Record<string, boolean>>

​client.evaluateAB(keys, userId, attributes?): Promise<Record<string, boolean>>

​Secrets (secret key only)

​client.getSecret(key: string): string

​client.getSecretFilePath(key: string): string | undefined

​Write API (secret key only)

​client.setSecret(key: string, value: string): Promise<void>

​client.deleteSecret(key: string): Promise<void>

​client.deleteSecretVersion(key: string, version: number): Promise<void>

​Metadata

​Sync / lifecycle

​client.connectStream() / client.disconnectStream()

​client.close(): Promise<void>

​Error types

Construction

`NexusClient.create(config: NexusConfig): Promise<NexusClient>`

Configs

`client.getConfig(key: string): string | undefined`

`client.getAllConfigs(): Record<string, string>`

Feature flags

`client.getFlag(key: string, defaultValue?: boolean): boolean`

`client.getAllFlags(): Record<string, boolean>`

`client.evaluateFlags(keys: string[]): Promise<Record<string, boolean>>`

`client.evaluateAB(keys, userId, attributes?): Promise<Record<string, boolean>>`

Secrets (secret key only)

`client.getSecret(key: string): string`

`client.getSecretFilePath(key: string): string | undefined`

Write API (secret key only)

`client.setSecret(key: string, value: string): Promise<void>`

`client.deleteSecret(key: string): Promise<void>`

`client.deleteSecretVersion(key: string, version: number): Promise<void>`

Metadata

Sync / lifecycle

`client.connectStream()` / `client.disconnectStream()`

`client.close(): Promise<void>`

Error types