Azure Functions for JavaScript Developers

1. Install Core Tools — npm i -g azure-functions-core-tools@4 2. Create function — func new --template "HTTP Trigger" --name GetUser 3. v4 model — register app, define routes with app.http() in src/functions/*.ts 4. Cosmos DB binding — input binding auto-fetches doc, no SDK code needed 5. Local dev — func start (emulator for Cosmos DB, Storage, SignalR) 6. Deploy — func azure functionapp publish myapp (or VS Code extension) 7. Application Insights — auto-instrumented, logs + traces + metrics free 8. CI/CD — GitHub Action with azure/functions-action on push to main

// src/functions/getUser.ts — v4 programming model import { app, HttpRequest, HttpResponseInit, InvocationContext } from "@azure/functions"; import { input } from "@azure/functions"; app.http("getUser", { methods: ["GET"], route: "users/{id}", authLevel: "anonymous", extraInputs: [ input.cosmosDB({ databaseName: "mydb", collectionName: "users", id: "{id}", partitionKey: "{id}", connection: "COSMOS_CONN", }), ], handler: async (req: HttpRequest, ctx: InvocationContext): Promise<HttpResponseInit> => { const user = ctx.extraInputs.get("user"); if (!user) return { status: 404, jsonBody: { error: "User not found" } }; return { jsonBody: user }; }, }); // host.json — runtime config { "version": "2.0", "extensionBundle": { "id": "Microsoft.Azure.Functions.ExtensionBundle", "version": "[4.0.0, 5.0.0)" }, "logging": { "applicationInsights": { "samplingSettings": { "isEnabled": true, "maxTelemetryItemsPerSecond": 20 } } } }