MSDN Documentation

Prerequisites

Before you begin, ensure you have the following installed on your development machine:

• Node.js: Download and install the latest LTS version from nodejs.org.
• Azure Functions Core Tools: Install globally using npm:

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

• Azure CLI (Optional but Recommended): For easier deployment and management of Azure resources. Install from Microsoft Docs.

Installation and Setup

Once you have the prerequisites, you can create your first Azure Functions project.

1. Create a new directory for your project and navigate into it:

   mkdir MyAzureFunctionsProject
   cd MyAzureFunctionsProject

2. Initialize a new Azure Functions project:

   func init --worker-runtime node

   This command creates a basic project structure with essential configuration files like local.settings.json and host.json.

HTTP Triggers

HTTP triggers allow your functions to be invoked via HTTP requests. They are commonly used for building APIs.

To create an HTTP-triggered function:

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

This creates a new folder MyHttpTrigger containing index.js and function.json. The index.js file will contain your Node.js code:

// MyHttpTrigger/index.js
module.exports = async function (context, req) {
    context.log('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. Pass a name in the query string or in the request body for a personalized response.';

    context.res = {
        // status: 200, /* Defaults to 200 */
        body: responseMessage
    };
};

The function.json file defines the trigger and its configuration:

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

Timer Triggers

Timer triggers execute your function on a schedule defined by a CRON expression. This is useful for background tasks.

Create a timer trigger:

func new --template "Timer trigger" --name MyTimerTrigger

Example index.js:

// MyTimerTrigger/index.js
module.exports = async function (context, myTimer) {
    const timeStamp = new Date().toISOString();
    if (myTimer.isPastDue) {
        context.log('JavaScript is running late!');
    }
    context.log('JavaScript timer trigger function executed at', timeStamp);
};

The CRON schedule is defined in function.json:

// MyTimerTrigger/function.json
{
  "scriptFile": "index.js",
  "bindings": [
    {
      "name": "myTimer",
      "type": "timerTrigger",
      "direction": "in",
      "schedule": "0 */5 * * * *" // Runs every 5 minutes
    }
  ]
}

Queue Triggers

Queue triggers execute your function when a message is added to a specified Azure Storage Queue.

Create a queue trigger:

func new --template "Azure Queue Storage trigger" --name MyQueueTrigger

Example index.js:

// MyQueueTrigger/index.js
module.exports = async function (context, myQueueItem) {
    context.log('JavaScript queue trigger function processed work item', myQueueItem);
    context.log('Queue item content: ', myQueueItem);
};

The queue connection string and name are configured in function.json and local.settings.json:

// MyQueueTrigger/function.json
{
  "scriptFile": "index.js",
  "bindings": [
    {
      "name": "myQueueItem",
      "type": "queueTrigger",
      "direction": "in",
      "queueName": "myqueue-items",
      "connection": "AzureWebJobsStorage"
    }
  ]
}

Input Bindings

Input bindings allow you to read data from a service and make it available as parameters in your function.

Example: Retrieving a document from a Cosmos DB collection.

// In function.json
{
  "bindings": [
    // ... other bindings
    {
      "name": "inputDocument",
      "type": "cosmosDB",
      "direction": "in",
      "databaseName": "Tasks",
      "collectionName": "Items",
      "id": "{queueTrigger}", // Example: get ID from a queue trigger
      "connectionStringSetting": "CosmosDbConnectionString"
    }
  ]
}

// In index.js
module.exports = async function (context) {
    const document = context.bindings.inputDocument;
    context.log('Retrieved document:', document);
};

Output Bindings

Output bindings enable your function to write data to a service.

Example: Sending a message to an Azure Service Bus queue.

// In function.json
{
  "bindings": [
    // ... other bindings
    {
      "name": "outputSbMessage",
      "type": "serviceBus",
      "direction": "out",
      "queueName": "output-queue",
      "connection": "ServiceBusConnection"
    }
  ]
}

// In index.js
module.exports = async function (context) {
    context.bindings.outputSbMessage = { body: "Hello from Azure Functions!" };
    context.log('Message sent to Service Bus.');
};