Building a simple REST API with Azure Functions V4

Welcome to this guide on building a REST API with Azure Functions V4. In this guide, we’ll walk through the steps to create a simple CRUD API using TypeScript, Visual Studio Code, and Azure Table Storage. This hands-on tutorial is suitable for both beginners and experienced developers, offering a quick path to creating your API on the Azure platform.

I chose Azure Table Storage for this tutorial because this is one of the easiest ways to store data in Azure with low costs (pricing details) compared to a database. If you do not want to use Azure Table Storage, then you can change the implementation of the function app to any kind of storage provider like an SQL database or Cosmos DB.

Step 1: Create resource group (optional)

If you do not have a resource group yet or want to clear the resources of this tutorial easily, then creating a resource group is needed.

• In the Azure portal, navigate to “Resource groups”
• In the top left, click on the “Create” button
• In the “Basics” tab, enter:
  • Resource group: “<your resource group>”
  • Region: “<your region>”
  • Click “Review + create”
• In the “Review” tab, click on “Create”

Step 2: Create storage account

In this step we will create the storage account for the storage table and copy the connection string for step 4.

Create storage account:

• In the Azure portal, navigate to “Storage accounts”



• In the top left, click on the “Create” button
• In the “Basics” tab, enter:
  • Resource group: “<your resource group>”
  • Storage account name: “<any name>”
  • Region: “<your region>”
  • Performance: “Standard”
  • Redundancy: “Locally-redundant storage (LRS)”
  • Click “Review” on the bottom left
• In the “Review” tab, wait for validation, then click on “Create”

Your storage account will now be created. This can take a moment.

After the deployment is completed, click on “Go to resource”.

Copy connection string:

• On the left, click on “Access keys”
• Under “key1”, click on “Show” after the Connection string
• Click the small “Copy to clipboard” button and save the string to a text file for the configuration of the function app in step 4, the connection string starts with “DefaultEndpointsProtocol=https;AccountName=”

Step 3: Create table in the storage account

In this step we will create the table to store the data.

• In the Azure portal, navigate to “Storage browser”
• Select the storage account which was created in the previous step
• On the left, click on “Tables”
• Click on “Add table”
• In the dialog, enter “things” and click on “Ok”

Your table is now created and ready for some things.

Step 4: Create function app

In this step we will create and configure the function app.

Create function app:

• In the Azure portal, navigate to “Function App”



• In the top left, click on the “Create” button
• In the “Basics” tab, enter:
  • Resource Group: “<your resource group>”
  • Function App name “<any name>”
  • Runtime stack: “Node.js”
  • Version: “18 LTS”
  • Region: “<your region>”
  • Operating System: “Linux”
  • Hosting options and plans: “Consumption”
  • Click “Review + create”
• In the “Review” tab, wait for validation, then click on “Create”

Your function app will now be created. This can take a moment.

After the deployment is completed, click on “Go to resource”.

Configure function app:

• On the left, click on “Configuration” under “Settings”
• Under “Application settings”, click on “New application setting”
  • Name: “DATA_TABLE_CONNECTION_STRING”
  • Value: “<the storage account connection string from step 2>”
  • Click “Ok”
• Click “New application setting” again
  • Name: “DATA_TABLE_NAME”
  • Value: “things”
  • Click “Ok”
• On the top bar, click on “Save”
• Click “Continue” in the confirmation dialog to save the changes

Step 5: Clone the example app with VS Code

In this step we clone the example app to VS Code. Copy the string below.

https://github.com/allardvanderouw-amis/azure-function-app-rest-example.git

This is a modified version of the “Create Function” code of the “Azure Functions” VS Code extension.

• In VS Code, click on “Source Control” in the left menu bar
• Click on “Clone Repository”
• Paste the GitHub string
• Press Enter and select a destination folder
• After completion click on “Open” in the dialog to open the repository in VS Code

You have now cloned the example app to your local environment.

The folder structure is:

<project_root>/
 | - .vscode/
 | - dist/
 | - node_modules/
 | - src/
 | | - common/
 | | | - tableClient.ts
 | | - functions/
 | | | - createThing.ts
 | | | - deleteThing.ts
 | | | - getThing.ts
 | | | - getThings.ts
 | | | - updateThing.ts
 | | - index.ts
 | - .funcignore
 | - .gitignore
 | - host.json
 | - package-lock.json
 | - package.json
 | - README.json
 | - tsconfig.json

The “functions” folder contains all the function files which contain the logic behind the functions, like the interaction with the table storage.

The “src/index.ts” file contains the function app routes:

import { app } from "@azure/functions";
import { createThing } from "./functions/createThing";
import { deleteThing } from "./functions/deleteThing";
import { getThing } from "./functions/getThing";
import { getThings } from "./functions/getThings";
import { updateThing } from "./functions/updateThing";

app.http("getThings", {
  methods: ["GET"],
  authLevel: "anonymous",
  route: "things",
  handler: getThings,
});

app.http("createThing", {
  methods: ["POST"],
  authLevel: "anonymous",
  route: "things",
  handler: createThing,
});

app.http("getThing", {
  methods: ["GET"],
  authLevel: "anonymous",
  route: "things/{id}",
  handler: getThing,
});

app.http("updateThing", {
  methods: ["PUT"],
  authLevel: "anonymous",
  route: "things/{id}",
  handler: updateThing,
});

app.http("deleteThing", {
  methods: ["DELETE"],
  authLevel: "anonymous",
  route: "things/{id}",
  handler: deleteThing,
});

This way of the defining the functions is the main difference compared to Azure Functions V3.

Now we will deploy the app to the created function app.

Step 6: Deploy the example app to the function app

In this step we will deploy the example app to Azure.

Setup VS Code for Azure:

In VS Code, click on “Extensions” in the left menu bar. Install the following Microsoft extensions:

• Azure Account
• Azure Functions
• Azure Resources

Sign in to Azure:

After installing these extensions, there should be an Azure button in the left bar. Click on it.

Then click on “Sign in to Azure…”. This should open a browser which prompts you to sign in to Azure. Sign in and close the window.

On the left, you should now see your Azure resources.

Initialize function app:

• On the bottom left of the Azure tab, click on “Local Project”
• Click on “Initialize Project for Use with VS Code…”

The local project is now initialized.

Deploy function app:

• On the bottom left of the Azure tab, click on the tiny Function App logo (it is shown when the workspace subwindow has focus or on mouse-over)



• Click on “Deploy to function app…”
• In the top center, a small dialog appears showing ‘Loading…’
• After loading is completed, select the function app which you have created earlier, then press “Enter”



• A dialog appears to confirm overwrite, press “Deploy”
• The deployment has started and should finish successfully, then click on “Show output” on the bottom right (or on the output-tab)

The output should show the trigger URLs:

These are the URLs which are now available. Great, time for some actual testing.

Step 7: Test the function app

So everything is ready to go now. Time to get things going.

To test the function app easily, an API client like Postman is suggested.

Get things

Request URL:

GET https://<your function app name>.azurewebsites.net/api/things

Response body:

[ ]

Makes sense, because we haven’t created any things yet.

Create a thing

Request URL:

POST https://<your function app name>.azurewebsites.net/api/things

Request body:

{
  "name": "Special thing",
  "description": "This is a special thing..."
}

Click “Send” to create the first thing.

Create another one:

Request body:

{
  "name": "Another special thing",
  "description": "This is another special thing..."
}

Get things (again)

Request URL:

GET https://<your function app name>.azurewebsites.net/api/things

(if you are using Postman, make sure the body is set to “none” on GET requests, else an error is shown)

Response body:

[
  {
    "etag": "W/\"datetime'2023-10-22T13%3A39%3A59.1889147Z'\"",
    "partitionKey": "71d5adad-c8b7-4ef3-8ab2-2d82eaacbf69",
    "rowKey": "71d5adad-c8b7-4ef3-8ab2-2d82eaacbf69",
    "timestamp": "2023-10-22T13:39:59.1889147Z",
    "id": "71d5adad-c8b7-4ef3-8ab2-2d82eaacbf69",
    "name": "Another special thing",
    "description": "This is another special thing..."
  },
  {
    "etag": "W/\"datetime'2023-10-22T13%3A39%3A55.7808569Z'\"",
    "partitionKey": "8bad0780-4f03-4db7-a681-910cfea05c2c",
    "rowKey": "8bad0780-4f03-4db7-a681-910cfea05c2c",
    "timestamp": "2023-10-22T13:39:55.7808569Z",
    "id": "8bad0780-4f03-4db7-a681-910cfea05c2c",
    "name": "Special thing",
    "description": "This is a special thing..."
  }
]

In Azure you can also see the two things in the storage browser:

Get a single thing

Request URL:

GET https://<your function app name>.azurewebsites.net/api/things/<id of thing>

Response body:

{
  "odata.metadata": "https://saallardfav4api.table.core.windows.net/$metadata#things/@Element",
  "etag": "W/\"datetime'2023-10-22T13%3A39%3A59.1889147Z'\"",
  "partitionKey": "71d5adad-c8b7-4ef3-8ab2-2d82eaacbf69",
  "rowKey": "71d5adad-c8b7-4ef3-8ab2-2d82eaacbf69",
  "timestamp": "2023-10-22T13:39:59.1889147Z",
  "id": "71d5adad-c8b7-4ef3-8ab2-2d82eaacbf69",
  "name": "Another special thing",
  "description": "This is another special thing..."
}

Update a thing

Request URL:

PUT https://<your function app name>.azurewebsites.net/api/things/<id of thing>

Request body:

{
  "name": "Modified special thing",
  "description": "This is modified special thing..."
}

Response body:

{
  "partitionKey": "71d5adad-c8b7-4ef3-8ab2-2d82eaacbf69",
  "rowKey": "71d5adad-c8b7-4ef3-8ab2-2d82eaacbf69",
  "name": "Modified special thing",
  "description": "This is modified special thing..."
}

The thing is now modified. You can review this through a GET request or with the storage browser.

Delete a thing

Request URL:

DELETE https://<your function app name>.azurewebsites.net/api/things/<id of thing>

Response:

204 No Content

The thing is now deleted. You can review this through a GET request or with the storage browser.

Step 8: Celebrate

If you got here without any (big) issues. Then it is time to celebrate to completion of this tutorial!

🎂 🎉 🥳

Step 9: Clear resources (optional)

• In the Azure portal, navigate to “Resource groups”
• If you created a fresh resource group, you can simply delete the resource group from here
• Else you can clear the newly created resources, see the image below for the resources which are created during this tutorial

Wrapping it up

In conclusion, this tutorial has walked you through the process of creating a REST API using Azure Functions V4, TypeScript, VS Code, and Azure Table Storage. We’ve covered the following steps:

• Creating a resource group (optional) to manage your tutorial resources.
• Setting up a storage account to store your data.
• Creating a table within the storage account to hold your data.
• Creating and configuring a function app to host your REST API.
• Cloning the example app to your local environment using VS Code.
• Deploying the example app to your function app in Azure.
• Testing your function app with various API calls, including getting, creating, updating, and deleting “things.”
• Celebrating your successful completion of the tutorial.

Once you’ve completed all the steps and tested your REST API, you can choose to clear the tutorial resources to keep your Azure environment tidy.

If you have any questions or need further assistance, feel free to reach out for help. Good luck with your future Azure development projects!