React Native 0.60+模拟器点击链接打开主机浏览器原理咨询

Great question! Let's break down exactly what's happening here step by step:

1. The openURLInBrowser function talks to React Native's own dev server #

First, let's look at the target of that fetch call: getDevServer().url + 'open-url' — this points to React Native's local development server (the one running at http://localhost:8081 when you start your app with npm start or yarn start), not a third-party backend API.

2. The dev server has a special handler for the open-url endpoint #

When the dev server receives this POST request (with the target URL in the request body), it doesn't send back JSON or data like a typical API would. Instead, it runs a system-level command on your host machine to open the URL:

• On macOS, it executes the open command
• On Windows, it uses the start command
• On Linux, it calls xdg-open

These commands tell your host operating system to launch its default browser and load the provided URL — that's why the link opens on your computer, not the simulator or physical device.

3. Fetch is just an HTTP client (the magic is in the server, not fetch) #

You're right that fetch is commonly used to communicate with backend APIs, but at its core, it's just a tool for sending HTTP requests to any server that speaks HTTP. The behavior you're seeing has nothing to do with fetch itself — it's entirely about what the React Native dev server is programmed to do when it receives that specific open-url request.

Think of it this way: if you sent a fetch request to a server set up to send you a cat image, fetch would just deliver that image back. Here, the server is set up to trigger a system action instead of returning data.

内容的提问来源于stack exchange，提问作者Isaac