angular-cn/packages/platform-server/init/PACKAGE.md

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feat(platform-server): allow shimming the global env sooner (#40559) `@angular/platform-server` provides the foundation for rendering an Angular app on the server. In order to achieve that, it uses a server-side DOM implementation (currently [domino][1]). For rendering on the server to work as closely as possible to running the app on the browser, we need to make DOM globals (such as `Element`, `HTMLElement`, etc.), which are normally provided by the browser, available as globals on the server as well. Currently, `@angular/platform-server` achieves this by extending the `global` object with the DOM implementation provided by `domino`. This assignment happens in the [setDomTypes()][2] function, which is [called in a `PLATFORM_INITIALIZER`][3]. While this works in most cases, there are some scenarios where the DOM globals are needed sooner (i.e. before initializing the platform). See, for example, #24551 and #39950 for more details on such issues. This commit provides a way to solve this problem by exposing a side-effect-ful entry-point (`@angular/platform-server/init`), that shims the `global` object with DOM globals. People will be able to import this entry-point in their server-rendered apps before bootstrapping the app (for example, in their `main.server.ts` file). (See also [#39950 (comment)][4].) In a future update, the [`universal` schematics][5] will include such an import by default in newly generated projects. [1]: https://www.npmjs.com/package/domino [2]: https://github.com/angular/angular/blob/0fc8466f1be392917e0c/packages/platform-server/src/domino_adapter.ts#L17-L21 [3]: https://github.com/angular/angular/blob/0fc8466f1be392917e0c/packages/platform-server/src/server.ts#L33 [4]: https://github.com/angular/angular/issues/39950#issuecomment-747598403 [5]: https://github.com/angular/angular-cli/blob/cc51432661eb4ab4b6a3/packages/schematics/angular/universal PR Close #40559
2021-02-11 12:24:52 -05:00
Initializes the server environment for rendering an Angular application.
For example, it provides shims (such as DOM globals) for the server environment.
The initialization happens as a [side effect of importing](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/import#import_a_module_for_its_side_effects_only) the entry point (i.e. there are no specific exports):
```ts
import '@angular/platform-server/init';
```
<div class="alert is-important">
The import must come before any imports (direct or transitive) that rely on DOM built-ins being available.
</div>