A development team I worked with in Seattle had a Node.js API that only needed to run a few times an hour, processing uploaded invoices and writing results to a database. They were paying for an always-on App Service plan just to handle that light, unpredictable traffic. Once we rebuilt the workload as a TypeScript-based function, the same job ran on true consumption pricing and their monthly compute cost dropped by more than half.
That’s the exact situation where Azure Function TypeScript development earns its place in a modern architecture. TypeScript gives you compile-time type safety and better tooling than plain JavaScript, while Azure Functions gives you event-driven, serverless compute that only bills for actual execution time.
Together, they’re a strong fit for APIs, background processing, and integration workloads that don’t need a server running around the clock.
In this guide, I’ll walk through setting up an Azure Function using TypeScript from scratch, covering project structure, identity and secret management, deployment through CI/CD, and the monitoring and cost decisions that separate a hobby project from a production-ready service.
Azure Function TypeScript
Why TypeScript for Azure Functions
Azure Functions is Microsoft’s serverless compute service, where code runs in response to triggers like HTTP requests, timers, queue messages, or blob storage events, and you pay only for the compute consumed during execution. Writing those functions in TypeScript — a statically typed superset of JavaScript that compiles down to plain JavaScript — adds a layer of safety that plain JavaScript doesn’t give you.
I switched most of my Node-based function projects to TypeScript a few years ago after a production incident where an untyped function silently passed undefined into a database call and failed at 2 a.m. with a vague error.
TypeScript catches that kind of mistake at build time instead of runtime, which matters a lot when a function is triggered by an external system and nobody’s watching it execute in real time.
The trade-off is a slightly heavier build process. TypeScript functions require a compilation step before deployment, and you need to manage a tsconfig.json file and build output directory correctly, or your function app won’t find the compiled code.
It’s a small amount of added complexity in exchange for fewer runtime surprises, and in my experience, that trade is worth it for anything beyond a quick throwaway script.
Pro Tip: I’ve seen more failed function deployments caused by a misconfigured build output path than by any actual code bug. Get the
tsconfig.jsonoutput directory right before you touch anything else.
Choosing the Right Hosting Plan
Before writing any code, decide how the function app will be hosted, because this choice affects cost, scaling behavior, and cold start performance. Azure Functions offers three main hosting models, and picking the wrong one is one of the most common mistakes I see teams make early on.
| Hosting Plan | Billing Model | Best For |
|---|---|---|
| Consumption | Pay per execution and GB-seconds | Unpredictable or infrequent workloads |
| Premium | Pre-warmed instances, billed hourly | Workloads needing no cold starts or VNet integration |
| Dedicated (App Service Plan) | Fixed hourly VM cost | Steady, high-frequency workloads already on App Service |
The Consumption plan is the default choice for most new projects because it scales to zero when idle and charges nothing during downtime. The trade-off is cold starts — a delay when a function wakes up from an idle state to handle a new request. For the invoice-processing example I mentioned earlier, a few seconds of cold start didn’t matter since it wasn’t user-facing.
If your function serves a real-time API where a two-to-five-second delay is unacceptable, look at the Azure Functions Premium plan, which keeps a minimum number of instances warm and supports virtual network integration for private connectivity to backend resources.
For workloads with more predictable, constant traffic, the Azure Functions Dedicated plan runs on the same App Service Plan infrastructure you might already be using for a web app, which can simplify cost management if you’re consolidating resources on plans you already pay for.
Pro Tip: I default every new TypeScript function project to Consumption plan pricing first, then only move to Premium if cold starts actually cause a measurable problem in testing. Too many teams over-provision for a cold start issue they never co