How to build functions

Explore how to develop and debug serverless Functions using JavaScript on the Azion Runtime, enhancing your Applications.

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Before you begin

To get started and excel as an edge developer, it’s important to:

Azion Functions works on the Azion Runtime, which is a set of tools that enable the development.

It’s paramount to take a look at the list of available APIs, methods, and types. Learn more about Azion Runtime.

Code Editor

The Functions Code Editor provides a development experience similar to what developers are accustomed to. The Functions ChatGPT Integration helps you to write, refactor, and review code.

Functions and Applications

To develop your first function for Applications:

  1. Access Azion Console > Functions.
  2. Click + Function.
  3. Choose a name for your function.
  4. Write your function. But wait, before that, keep reading:

Writing an function

First, the functions for applications work based on a fetch event. It’s initialized with an addEventListener function, passing fetch as the event type, and an event. For example:

addEventListener('fetch', event => {
event.respondWith(handleRequest(event.request));
});

Second, it’s necessary to define the behavior of the handleRequest function. This function has the event.request as the signature. This data can be used later on to implement the necessary logic, such as:

  • Manipulate cookies.
  • Implement a behavior based on the request method (POST, GET, PUT, DELETE).
  • Access request metadata.

The handleRequest function can be defined as:

const html = `<!DOCTYPE html>
<body>
<h1>Hello World</h1>
<p>This markup was generated by Azion - Functions.</p>
</body>`
async function handleRequest(request) {
return new Response(html, {
headers: {
"content-type": "text/html;charset=UTF-8",
},
})
}

In this example, the response will be the HTML content, declared previously by the const html. The headers can be manipulated as well, and in the example, the content type is set.

  1. Click the Save button.

Testing and Debugging

After writing your functions, you can preview the response and inspect the code. The preview simulates a request, and this simulation can be altered to meet the developer’s needs.

Learn more about Azion Preview Deployment.

It’s possible to debug the functions through:

Function instantiation

Once you’ve saved your function, it’s necessary to instantiate it in an application.

Learn more on how to instantiate a function on Applications.