Edge Computing with Cloudflare Workers & Deno · レッスン

HTTPリクエストの処理

HTTPリクエストをインターセプトして応答する基本的なWorkerを作成し、中核的な機能を確認します。

「HTTPリクエストの処理」はCoddyKit上の無料Edge Computing with Cloudflare Workers & Denoレッスンです。これはレッスン2/4です。下記で完全なレッスンを無料で読むことができます。その後、ブラウザ内の組み込みコードエディタと24時間対応のAIチューターでハンズオン演習できます。これはEdge Computing with Cloudflare Workers & Deno学習パスの一部であり、ウェブとCoddyKitアプリ全体で進捗が同期されます。 Edge Computing with Cloudflare Workers & Denoコースには全4レッスンが含まれています。

このレッスンの一部はまだ翻訳されておらず、英語で表示されています。

Workers and Web Requests

Cloudflare Workers are powerful tools that sit at the edge of the internet. Think of them as highly efficient gatekeepers for your web traffic.

Their primary job is to intercept incoming HTTP requests, process them using your code, and then send back an appropriate HTTP response.

Understanding the Request

Every time a user's browser interacts with your Worker, it receives a Request object. This object is packed with all the details about the incoming request:

URL: The full web address the user tried to reach.
Method: The HTTP action, like GET (fetching data) or POST (sending data).
Headers: Extra information such as the browser type, cookies, and preferred language.
Body: Any data sent with the request, common with POST or PUT methods.

Catching the Fetch Event

Cloudflare Workers use an event listener to 'catch' incoming requests. The fetch event is triggered for every HTTP request that hits your Worker.

The standard entry point for a Worker is an exported object with an async fetch method. This method receives the request object as its first argument.

export default {
  async fetch(request, env, ctx) {
    // Your Worker logic goes here
    // The 'request' object holds all incoming request details
    return new Response("Hello from Worker!");
  }
}

Crafting a Simple Response

After your Worker processes a request, it needs to send back a Response object. This object contains the content and metadata that the user's browser will receive.

A basic Response can be created by simply passing a string of text to its constructor.

export default {
  async fetch(request, env, ctx) {
    const responseText = "Welcome to the edge!";
    return new Response(responseText);
  }
}

Your First 'Hello Worker!'

Let's combine what we've learned to create a simple Worker that says "Hello Cloudflare Worker!" to every incoming request.

This is the fundamental structure you'll use for almost all Cloudflare Workers.

export default {
  async fetch(request, env, ctx) {
    return new Response("Hello Cloudflare Worker!");
  }
}

Peeking at the Request URL

You can access various properties of the request object to get information about the incoming request. For example, request.url gives you the full URL that was requested.

This allows you to create dynamic responses based on the specific path or query parameters a user is trying to reach.

export default {
  async fetch(request, env, ctx) {
    const url = request.url;
    return new Response(`You requested: ${url}`);
  }
}

Responding to GET vs. POST

The request.method property tells you the HTTP method used (e.g., GET, POST, PUT, DELETE). You can use this to provide different logic for different types of requests.

For instance, a GET request might fetch data, while a POST request might submit data for creation.

export default {
  async fetch(request, env, ctx) {
    if (request.method === "GET") {
      return new Response("This is a GET request.");
    } else if (request.method === "POST") {
      return new Response("This is a POST request.", { status: 201 });
    }
    return new Response("Method not allowed.", { status: 405 });
  }
}

Custom Headers and Status

You can customize the Response object further by adding HTTP headers or changing the status code. This is done by passing an options object as the second argument to the Response constructor.

Headers: Provide metadata about the response (e.g., Content-Type: text/plain).
Status Code: Indicates the outcome of the request (e.g., 200 OK, 404 Not Found).

export default {
  async fetch(request, env, ctx) {
    return new Response("Custom response!", {
      status: 200,
      headers: {
        "Content-Type": "text/plain",
        "X-Worker-Info": "Processed at the Edge"
      }
    });
  }
}

Fetching from an Origin

Often, your Worker will act as a proxy. This means it fetches content from an 'origin server' (your actual website or API backend) and potentially modifies it before sending it to the user.

You can use the global fetch() function, passing it the original request object, to forward the request to another server.

export default {
  async fetch(request, env, ctx) {
    // Fetch the request from the origin server
    const response = await fetch(request);
    // You can modify the response here before returning it
    return response;
  }
}

Worker Response Check

You're building a Cloudflare Worker. Which of the following correctly sets the status code of a response to 404 Not Found?

Recap: Handling HTTP Requests

In this lesson, you learned the core of Cloudflare Workers: how they handle HTTP requests and send back responses.

Workers intercept fetch events.
The Request object contains all incoming request data.
You return a Response object to the user.
You can access request details like URL and method.
Responses can have custom status codes and headers.
Workers can act as proxies, fetching content from origin servers.

Next, you'll learn the steps to deploy your first Worker to Cloudflare's edge network so it can start serving users globally!

よくある質問

「HTTPリクエストの処理」レッスンは無料ですか？

はい。「HTTPリクエストの処理」の完全なテキストはこのウェブで無料で読めます。インタラクティブに演習し（組み込みコードエディタと24時間対応のAIチューター）、Edge Computing with Cloudflare Workers & Denoコースの残りをアンロックするには、CoddyKit PROにアップグレードしてください。 Edge Computing with Cloudflare Workers & Denoコースには全4レッスンが含まれています。

「HTTPリクエストの処理」で何を学びますか？

HTTPリクエストをインターセプトして応答する基本的なWorkerを作成し、中核的な機能を確認します。ブラウザで直接実行するハンズオンコードでEdge Computing with Cloudflare Workers & Denoを演習し、24時間対応のAIチューターがレッスンを進める中での質問に答えます。

Edge Computing with Cloudflare Workers & Denoを始めるのに経験は必要ですか？

事前経験は必要ありません。CoddyKitのEdge Computing with Cloudflare Workers & Denoは初級者から上級者向けに構成されているため、ここから始めるか最初から始めて、自分のペースで進むことができます。これはレッスン2/4です。

「HTTPリクエストの処理」レッスンにはどのくらい時間がかかりますか？

ほとんどのCoddyKitレッスンは約5～10分かかります。各レッスンはコンパクトでインタラクティブなので、着実に進歩し、ウェブとアプリ全体で正確に前回の場所から再開できます。

このEdge Computing with Cloudflare Workers & Denoレッスンでコードを書いて実行できますか？

はい。すべてのEdge Computing with Cloudflare Workers & Denoレッスンに組み込みコードエディタが含まれているため、ブラウザでリアルコードを書いて実行し、即座のAIフィードバックを取得できます。ローカル設定は不要です。

このコースのすべてのレッスン

← Edge Computing with Cloudflare Workers & Denoに戻る