Learn Bower, Browserify and Cloudflare

Cloudflare Workers let you write JavaScript Service Workers that run directly in Cloudflare's 200+ edge locations around the world.

With a Cloudflare Worker, you can modify your site's HTTP requests and responses, make parallel requests, and even reply directly from the edge.

Cloudflare Workers are written against a similar API to the W3C Service Workers standard. However, while Service Workers run inside the end user's browser, Cloudflare Workers run on Cloudflare's servers. This means that Cloudflare Workers can implement trusted code (which the client cannot tamper with), and will work no matter what browser the user is running.

In this course, Kristian Freeman will teach you how to build and deploy a Serverless API with Cloudflare Workers. By learning how to build your own serverless JSON APIs, you can effectively manage a highly-available backend for your projects, without needing to learn DevOps or manage services.

Cloudflare secures and ensures the reliability of your external-facing resources such as websites, APIs, and applications. It protects your internal resources such as behind-the-firewall applications, teams, and devices. And it is your platform for developing globally-scalable applications.

cloudflare

Build a Serverless API with Cloudflare Workers

Cloudflare Workers is a serverless application platform that enables you to create and deploy functions to Cloudflare's Edge Network.

Unlike other serverless providers that only have regional data centers, Cloudflare's Edge Network consists of hundreds of servers all over the world.

Cloudflare Workers is a powerful platform, and this course serves as a great introduction for what it can do.

Follow along with Kristian Freeman as you build a localization engine that renders data based on the Edge location nearest to the application's user.

After this course, you'll be ready to start experimenting with your own Cloudflare Workers projects. *Need an idea?* *[Check out the suggested Portfolio Project for this course.](https://egghead.io/projects/introduction-to-cloudflare-workers)*

Introduction to Cloudflare Workers

Gulp is a toolkit for automating painful or time-consuming tasks in your development workflow, so you can stop messing around and build something.

gulp

Building upon the `watch` task that we begin this lesson with, we’ll look at how to create a local development server using the `app` directory as the web root. By using Browsersync to achieve this, we can also instruct all connected browsers to automatically reload each time our bundle is re-generated. Browsersync has a public `.stream()` method that is designed exactly for this purpose.

Gulp and Browserify - Adding Live Reload with Browsersync

Babel has support for the latest version of JavaScript through syntax transformers. These plugins allow you to use new syntax, right now without waiting for browser support.

babel

What is already a nice workflow using Gulp, Browserify, Watchify & Browsersync to enable auto rebuilds & live browser reloading can be further improved by adding Babelify. A simple wrapper around the popular transpiler Babel, Babelify can ‘transform’ source files as they pass through our stream to enable certain Javascript features not yet available in the Browser or Node. We end the lesson by looking at how to generate & extract sourcemaps using `exorcist`.

Gulp and Browserify - Adding Babel & Source Maps

Browserify lets you require('modules') in the browser by bundling up all of your dependencies.

browserify

Let's look at the basics of setting up Gulp and Browserify. Creating a Gulp task from scratch, we'll cover how to utilise the Browserify API to generate a single `bundle.js` file, catch and log any errors that occur in the compilation process, transform the stream into a format that can be consumed by `gulp.dest` and finish by writing the bundle to a `dist` directory.

Gulp and Browserify - Initial Setup

Beginning with a single Gulp task capable of generating a one-time Browserify bundle, we enable file-watching and incremental rebuilds by incorporating Watchify. We add a second task `watch` & refactor our initial code to enable the bulk of it to be re-used. We’ll look at exactly how to ‘wire’ these tools together and how the relationship between Watchify & Browserify can manifest into a seriously efficient workflow.

Gulp and Browserify - Hooking up Watchify

bower

Bower is a package manager for Javascript libraries that allows you to define, version, and retrieve your dependencies. In this tutorial, John gives a quick introduction to Bower and will show you how to get started.

Introduction to Bower

To deploy a Cloudflare Workers serverless function, you'll need to sign up for a free Cloudflare Workers account at [workers.cloudflare.com](http://workers.cloudflare.com/), and select your unique workers.dev subdomain to deploy your functions to.

Create a Cloudflare Workers Account

Using NPM, you can install Cloudflare Workers' CLI (command-line interface), Wrangler, by typing `npm install -g @cloudflare/wrangler` into your command line. Wrangler allows you to generate and publish Cloudflare Workers projects. We'll also use the `wrangler login` command which will give you a link to authorize Wrangler. This will set up an API token specifically for your Wrangler installation that will allow you to publish and read all the Workers and Workers KV information that you need.

Install and Configure the Cloudflare Workers CLI Wrangler

Wranglers generate command, `wrangler generate`, allows you to create new Cloudflare Workers projects. Using the URL parameter, you can also generate new projects based on Cloudflare's starter templates, or open-source projects created by other developers, but for now, you will just use the default. To do this you'll only need to give it a name, for example, `wrangler generate my-worker`,  this will create a new project called my-worker. 

Generate New Cloudflare Workers Projects with Wrangler's generate Command

We'll take a look at the default code in `index.js` in a Workers project. We'll take a second to understand how it works before building the rest of our project. 

First will see what our Worker looks like in an actual browser by running `wrangler preview`. In a terminal, and we'll check out how Serverless functions in Cloudflare Workers listen for HTTPS requests via the "fetch" event and respond to them by creating and returning a new Response.

Write Your First Cloudflare Workers Serverless Function

Using `wrangler whoami` in a terminal we'll grab our account id so we can paste our id into the double quotes of `account_id = ""`  inside of `wrangler.toml` file. Using the `wrangler dev` command we can look at our Workers serverless function and test it before deploying it. Once we're ready to deploy, we can use the `wrangler publish` command to deploy it to our unique workers.dev subdomain.

Preview and Publish Your Cloudflare Workers Project

By updating the response body and setting a corresponding Content-Type header, we can render HTML pages from directly inside of our Cloudflare Workers function.

We will update our Cloudflare Worker to return a call to a template function that we define. That template function returns a string of HTML that we will render in the browser.

Render HTML Pages with Cloudflare Workers

Up until now, we've been rendering plain responses, not based on any information coming in with a request. The request.cf object sent with every incoming HTTP request to a Workers function has a ton of interesting information, including the regionality of the request, and which Cloudflare data center is responding to the request. Using this information, we'll render a dynamic HTML page based on where the user visiting our site is in the world.

Render Cloudflare Region Data for a Request Using request.cf

Deploying to your unique workers.dev subdomain is a great way to test your serverless functions before they're ready to go to production. Once you are ready to deploy to production, you can use Wrangler's environment feature to deploy to your zone, or Cloudflare-managed domain, by providing the "-e" (environment) flag when publishing.

You can check this worker out [here](https://hello-world-worker.signalnerve.com/).

Deploy to a Custom Domain with Cloudflare Wrangler Environments

The `Access-Control-Allow-Headers` response header is used in response to a preflight request which includes the `Access-Control-Request-Headers` to indicate which HTTP headers can be used during the actual request. 

In this lesson, we'll secure our API by building an allowlist of origins that can access our API, and update the CORS functionality in our code to adopt that allowlist when handling requests.

Secure an API with Access-Control-Allow-Headers

Cloudflare Pages is a JAMstack platform for frontend developers to collaborate and deploy websites. Cloudflare Pages is currently in open beta. 

In this lesson, we'll publish our frontend UI using Cloudflare Pages, Cloudflare's static site deployment tool.

Deploy a React Application Using Cloudflare Pages

In this lesson, we'll complete our React interface by taking the data from our Workers API and using it to render a collection of images, based on a search query.

Render Data from a Workers API Response in a React Application

CORS (Cross-Origin Resource Sharing) is a constraint of browser-based applications that provides extra security for APIs and servers. In this lesson, we'll set appropriate CORS headers for our Workers API, so that our frontend application is able to access it.

Add CORS Headers to a Third Party API Response in a Workers API

In this lesson, we'll parse the incoming data from Unsplash's API and transform it for our frontend client. Because Cloudflare Workers is serving as "middleware" - in-between the Unsplash API and our frontend client we'll build shortly - we can use it to format or simplify data coming through it that our client doesn't care about. We'll also use the Response class to return a JSON response from our API. JSON responses need to be formatted in a specific way to be able to be parsed by clients, so we'll look at the various pieces of a Response (body and headers) and how they work together to represent a JSON response.

Transform and Return JSON Data From an API in Cloudflare Workers

In this lesson, we'll use Workers Secrets to store our API credentials for Unsplash, an image API. This will allow us to safely deploy our application and publish it on GitHub without revealing any private keys or API tokens.

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