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Serverless API with Deno and Begin - Part 1

Paul Chin Jr.
Curious Human. #Serverless #JavaScript Dev @ http://arc.codes; Dev Rel at http://begin.com; Prophet of Nicolas Cage; #PraiseCage
Updated on ・4 min read

Deno is a runtime that can execute both JavaScript and TypeScript, which offers a very different development experience. Deno allows developers to write cloud functions with TypeScript without an explicit compile step or build tools.

Today we are going to deploy Deno as a serverless function with Begin. Along the way, we'll set up local development, describe how Deno is a little different from Node, and finally build an API endpoint that returns quotes from the famous actor, Nicolas Cage.
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Prerequisites

You can install Deno in a few different ways. I chose to install it with brew install deno, but you can check their docs for other methods.

You will also need Node, Git, and a Github account.

Try out a Deno Hello World example right now

Hit this button to deploy a new Hello World! Deno app to Begin in 15 seconds (no credit card required):

Deploy to Begin

Setting up local development

Begin creates a GitHub repo for your app. Go ahead and clone the repo and install dependencies.

git clone https://github.com/github-username/your-app.git
cd your-app
npm install
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We can then start Sandbox with an npm script. Sandbox is a local development server that exposes our functions to HTTP routes, just like API Gateway. It can also emulate DynamoDB, SNS events, and SQS queues.

npm start
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Once you get your local environment running, we can now start modifying the get-index function.

// src/http/get-index/index.ts
let quote = function() {
  let min = 0
  let max = quotes.length - 1
  let rando = ~~(Math.random() * (max-min) + min)
  return quotes[rando]
}
let quotes = [
"It's a family that's loaded with grudges and passion. We come from a long line of robbers and highwaymen in Italy, you know. Killers, even.",
"To be a good actor you have to be something like a criminal, to be willing to break the rules to strive for something new.",
"I think I jump around more when I'm alone.",
"I bought a Yamaha-1 and I was doing 180 miles per hour home on the 405 and that's really, really crazy but I did it.",
"I believe that being successful means having a balance of success stories across the many areas of your life. You can't truly be considered successful in your business life if your home life is in shambles."
]
export async function handler (req: object) {
  return {
    statusCode: 200,
    headers: {
     'content-type': 'text/html; charset=utf8',
     'cache-control': 'no-cache, no-store, must-revalidate, max-age=0, s-maxage=0'
    },
    body:`
    <!doctype html>
    <html lang=en>
    <head>
    <meta charset=utf-8>
    <title>Hi!</title>
    <link rel="stylesheet" href="https://static.begin.app/starter/default.css">
    <link href="data:image/x-icon;base64,iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAQAAAC1HAwCAAAAC0lEQVR42mNkYAAAAAYAAjCB0C8AAAAASUVORK5CYII=" rel="icon" type="image/x-icon">
    </head>
    <body><h1 class="center-text">Praise Cage</h1>
    <p class="center-text"><q>${quote()}</q></p>
    <div class="center-text"><img src="https://www.placecage.com/g/300/300"></div>
    <p class="center-text">Your <a href="https://begin.com" class="link" target="_blank">Begin</a> app is ready to go!</p
    </body>
    </html>`
   }
}
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quote() is a function. that returns a single random item from the quotes array. The handler() function executes each time a user requests the index route of your app. Its job is to call quote() and return an HTTP response with headers and an HTML string in the body.

Behind the scenes, you are working with an AWS Lambda function. Lambda functions are an event-driven, and stateless compute service. It has near-infinite scaling and doesn't requires traditional HTTP server configurations. The app.arc file in the root of your project defines all the routes under the @http pragma. Check out the docs for more info on project structure.

Using Deno as a custom Lambda runtime layer, we were able to write Typescript.

Look at what we have so far

Refresh http://localhost:3333 and check out your results! You can replace the quotes array with a different list of items, but I think Nicolas Cage is the best choice. #praisecage
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Deploy with CI/CD on Begin

Such a beautiful site deserves a good home on the web. Deploying this app is just one git push away. Every push to your default branch will start a new deployment to staging. Go ahead and show it off by sharing it with us on Twitter.

//todo: add API route

In the next post, we'll add a dedicated API route for other applications to take advantage of our quote machine. So stay tuned!

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