MSDN Documentation

Step 1: Setting Up Your Local Development Environment

Before you can create your serverless API, you need to set up your local environment. Install the Azure Functions Core Tools, which allow you to develop and test Azure Functions locally.

You can install the Core Tools using npm:

npm install -g azure-functions-core-tools@3 --unsafe-perm true

Verify the installation:

func --version

Step 2: Creating Your First Azure Function Project

Create a new folder for your project and navigate into it using your terminal. Then, initialize a new Azure Functions project.

mkdir MyServerlessApi
cd MyServerlessApi
func init --worker-runtime node

This command creates a new project with a `local.settings.json` file and a `host.json` file. The `--worker-runtime node` flag specifies that we'll be using Node.js for our functions.

Step 3: Creating an HTTP Triggered Function

Now, let's add an HTTP-triggered function to our project. This function will serve as the endpoint for our API.

func new --name MyHttpTrigger --template "HTTP trigger"

This command creates a new function named `MyHttpTrigger` with an HTTP trigger. You will find a new folder named `MyHttpTrigger` containing `index.js` and `function.json`.

Open `MyHttpTrigger/index.js` to see the default function code:

module.exports = async function (context, req) {
    context.log('JavaScript HTTP trigger function processed a request.');
    const name = (req.query.name || (req.body && req.body.name));
    const responseMessage = name
        ? 'Hello, ' + name + '. This HTTP triggered function executed successfully.'
        : 'This HTTP triggered function executed successfully. Pass a name in the query string or in the request body for a personalized response.';

    context.res = {
        body: responseMessage
    };
};

The `function.json` file defines the function's bindings (in this case, an HTTP input and output binding):

{
  "bindings": [
    {
      "authLevel": "function",
      "type": "httpTrigger",
      "direction": "in",
      "name": "req",
      "methods": [
        "get",
        "post"
      ]
    },
    {
      "type": "http",
      "direction": "out",
      "name": "res"
    }
  ]
}

Step 4: Running Your Function Locally

To test your function locally, start the Azure Functions host.

func start

The output will show the URL for your HTTP-triggered function. It will typically look something like this: http://localhost:7071/api/MyHttpTrigger

Open this URL in your browser or use a tool like Postman to send a GET request. Try adding a name query parameter, e.g.: http://localhost:7071/api/MyHttpTrigger?name=Alice

Step 5: Deploying Your Function to Azure

Once you're satisfied with your local testing, you can deploy your function app to Azure. First, ensure you are logged into your Azure account through the Azure CLI:

az login

Then, deploy your function project:

func azure functionapp publish 

Replace <YOUR_FUNCTION_APP_NAME> with a globally unique name for your function app. The Azure Functions extension in VS Code also provides a streamlined deployment experience.