How are Web APIs Integrated into JavaScript in Browsers?

In response to the original question, `fetch()` is actually a method of the `Window` class found in browser JavaScript environments. This means that when JavaScript runs in the browser, specific classes are included to give you access to these features—something you wouldn't see in server-side JavaScript.

Web APIs like `fetch()` aren't part of the ECMAScript specification; they come from how browsers implement JavaScript. There's no actual 'injection' happening; these APIs are built into the browser and come with the JavaScript environment available to you, just like other built-in functions.

The browser sets up an API for the JavaScript interpreter so it can connect to the browser environment. Essentially, when you write something like `fetch()`, it's not just standard JS—under the hood, the interpreter links to these browser-native functions. The specifics can vary, like how JS handles garbage collection differently from C++. For nerdy details, check out the embedding docs for V8, the engine behind Chrome!