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Node.js v4 Programming Model¶

This deep dive explains the Node.js v4 code-first model for Azure Functions. It covers registration APIs, trigger patterns, request and response handling, and practical composition patterns for production-ready apps.

Main Content¶

The v4 model removes per-function function.json authoring for normal scenarios and registers triggers directly in code.

flowchart TD
    A[Host starts] --> B["Load @azure/functions app object"]
    B --> C[Register app.http app.timer app.storageQueue app.storageBlob]
    C --> D[Index function metadata]
    D --> E[Accept trigger events]
    E --> F[Invoke handler with context]

Project Layout¶

project-root/
├── src/
│   └── functions/
│       ├── httpTrigger.js
│       ├── timerTrigger.js
│       └── queueTrigger.js
├── host.json
├── local.settings.json
└── package.json

HTTP Trigger Pattern¶

const { app } = require('@azure/functions');

app.http('helloHttp', {
    methods: ['GET'],
    authLevel: 'function',
    route: 'hello/{name?}',
    handler: async (request, context) => {
        const name = request.params.name || request.query.get('name') || 'world';
        context.log(`Request received for ${name}`);
        return {
            status: 200,
            jsonBody: {
                message: `Hello, ${name}`,
                model: 'nodejs-v4'
            }
        };
    }
});

Timer Trigger Pattern¶

const { app } = require('@azure/functions');

app.timer('cleanupTimer', {
    schedule: '0 */5 * * * *',
    handler: async (timer, context) => {
        context.log(`Timer fired at ${timer.scheduleStatus?.last || 'first-run'}`);
    }
});

Queue Trigger Pattern¶

const { app } = require('@azure/functions');

app.storageQueue('processOrders', {
    queueName: 'orders',
    connection: 'AzureWebJobsStorage',
    handler: async (queueItem, context) => {
        context.log(`Processing order ${queueItem.orderId}`);
    }
});

Blob Trigger Pattern¶

const { app } = require('@azure/functions');

app.storageBlob('ingestBlob', {
    path: 'incoming/{name}',
    connection: 'AzureWebJobsStorage',
    handler: async (blob, context) => {
        context.log(`Blob length: ${blob.length}`);
    }
});

ESM Variant¶

import { app } from '@azure/functions';

app.http('ping', {
    methods: ['GET'],
    handler: async (_request, context) => {
        context.log('Ping called');
        return { body: 'pong' };
    }
});

Request Data Access¶

Query: request.query.get('name')
Route params: request.params.name
Body JSON: await request.json()
Headers: request.headers.get('x-correlation-id')

Response Construction¶

JSON response: { status: 200, jsonBody: { ok: true } }
Text response: { status: 200, body: 'ok' }
Error response: { status: 400, jsonBody: { error: 'invalid-input' } }

Local Initialization¶

func init MyProject --worker-runtime node --language javascript --model v4
func new --template "HTTP trigger" --name httpTrigger
func start

See Also¶

Sources¶