89 lines
3.4 KiB
Markdown
89 lines
3.4 KiB
Markdown
# Using Web Workers with Angular CLI
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# 通过 Angular CLI 使用 Web Worker
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[Web Workers](https://developer.mozilla.org/en-US/docs/Web/API/Web_Workers_API) allow you to run CPU intensive computations in a background thread, freeing the main thread to update the user interface.
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[Web Workers](https://developer.mozilla.org/en-US/docs/Web/API/Web_Workers_API) 允许你在后台线程中运行 CPU 密集型计算，解放主线程，以便更新用户界面。
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If you find your application becomes unresponsive while processing data, using Web Workers can help.
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如果你发现你的应用在处理数据时停止了响应，那么使用 Web Workers 可以为你提供帮助。
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## Adding a Web Worker
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## 添加一个 Web Worker
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You can add a web worker anywhere in your application. If the file that contains your expensive computation is `src/app/app.component.ts`, you can add a Web Worker using `ng generate web-worker app`.
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你可以在应用中的任何地方添加一个 Web Worker。假设包含沉重计算工作的文件是 `src/app/app.component.ts`，你可以使用 `ng generate web-worker app` 新增一个 Web Worker。
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Running this command will:
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运行这个命令会：
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- configure your project to use Web Workers, if it isn't already.
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把你的项目配置成使用 Web Workers 的（如果尚未配置过）。
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- add `src/app/app.worker.ts` with scaffolded code to receive messages:
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添加 `src/app/app.worker.ts` 文件，并添加用于接收消息的脚手架代码：
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```typescript
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addEventListener('message', ({ data }) => {
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const response = `worker response to ${data}`;
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postMessage(response);
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});
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```
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- add scaffolded code to `src/app/app.component.ts` to use the worker:
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往 `src/app/app.component.ts` 中添加使用该 worker 的脚手架代码：
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```typescript
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if (typeof Worker !== 'undefined') {
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// Create a new
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const worker = new Worker('./app.worker', { type: 'module' });
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worker.onmessage = ({ data }) => {
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console.log('page got message: $\{data\}');
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};
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worker.postMessage('hello');
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} else {
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// Web Workers are not supported in this environment.
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// You should add a fallback so that your program still executes correctly.
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}
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```
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After the initial scaffolding, you will need to refactor your code to use the Web Worker by sending messages to and from.
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在完成了最初的脚手架之后，你需要重构代码，通过来回发送消息来使用 Web Worker。
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## Caveats
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## 警告
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There are two important things to keep in mind when using Web Workers in Angular projects:
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在 Angular 项目中使用 Web Workers 时，要记住两个重要事项：
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- Some environments or platforms, like `@angular/platform-server` used in [Server-side Rendering](guide/universal), don't support Web Workers. You have to provide a fallback mechanism to perform the computations that the worker would perform to ensure your application will work in these environments.
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某些环境或平台（比如[服务端渲染](guide/universal)中使用的 `@angular/platform-server` 不支持 Web Workers。你必须提供一个后备机制来执行 Worker 要执行的计算，以确保你的应用能在那些环境中运行。
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- Running Angular itself in a Web Worker via [**@angular/platform-webworker**](api/platform-webworker) is not yet supported in Angular CLI.
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Angular CLI 尚不支持通过 [**@angular/platform-webworker**](api/platform-webworker)在 Web Worker 中运行 Angular 自身。
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