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docs(zone.js): fix typos and align formatting (#35907) 

PR Close #35907
This commit is contained in:
Ferdinand Malcher 2020-03-06 13:39:16 +01:00 committed by Kara Erickson
parent 4d458db1b5
commit a5eb0e56b6
1 changed files with 51 additions and 52 deletions
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aio/content/guide/zone.md
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@ -47,7 +47,7 @@ To clarify how changes are detected and values updated, consider the following c
}
}
// example 1: update data inside button click event handler
// Example 1: update data inside button click event handler
document.getElementById('btn').addEventListener('click', () => {
// update value
value = 'button update value';
@ -55,7 +55,7 @@ To clarify how changes are detected and values updated, consider the following c
detectChange();
});
// example 2: Http Request
// Example 2: HTTP Request
const xhr = new XMLHttpRequest();
xhr.addEventListener('load', function() {
// get response from server
@ -66,7 +66,7 @@ To clarify how changes are detected and values updated, consider the following c
xhr.open('GET', serverUrl);
xhr.send();
// example 3: setTimeout
// Example 3: setTimeout
setTimeout(() => {
// update value inside setTimeout callback
value = 'timeout update value';
@ -74,18 +74,18 @@ To clarify how changes are detected and values updated, consider the following c
detectChange();
}, 100);
// example 4: Promise.then
Promise.resolve('promise resolved a value').then((v) => {
// Example 4: Promise.then
Promise.resolve('promise resolved a value').then(v => {
// update value inside Promise thenCallback
value = v;
// call detectChange manually
detectChange();
}, 100);
// example 5: some other asynchronous APIs
// Example 5: some other asynchronous APIs
document.getElementById('canvas').toBlob(blob => {
// update value when blob data is created from the canvas
value = `value updated by canvas, size is ${blog.size}`;
value = `value updated by canvas, size is ${blob.size}`;
// call detectChange manually
detectChange();
});
@ -108,7 +108,7 @@ To understand how change detection works, first consider when the application ne
<code-example path="user-input/src/app/click-me.component.ts" region="click-me-component" header="src/app/click-me.component.ts"></code-example>
3. Http Data Request. You can also get data from a server through an Http request. For example:
3. HTTP Data Request. You can also get data from a server through an HTTP request. For example:
```typescript
@Component({
@ -129,7 +129,7 @@ export class AppComponent implements OnInit {
}
```
4. MacroTasks, such as `setTimeout()`/`setInterval()`. You can also update the data in the callback function of `macroTask` such as `setTimeout()`. For example:
4. MacroTasks, such as `setTimeout()` or `setInterval()`. You can also update the data in the callback function of a `macroTask` such as `setTimeout()`. For example:
```typescript
@Component({
@ -148,7 +148,7 @@ export class AppComponent implements OnInit {
}
```
5. MicroTask, such as `Promise.then()`. Other asynchronous APIs return a Promise object (such as `fetch`), so the `then()` callback function can also update the data. For example:
5. MicroTasks, such as `Promise.then()`. Other asynchronous APIs return a Promise object (such as `fetch`), so the `then()` callback function can also update the data. For example:
```typescript
@Component({
@ -167,27 +167,23 @@ export class AppComponent implements OnInit {
}
```
6. Other async operations. In addition to `addEventListener()`/`setTimeout()`/`Promise.then()`, there are other operations that can update the data asynchronously. Some examples include `WebSocket.onmessage()` and `Canvas.toBlob()`.
6. Other async operations. In addition to `addEventListener()`, `setTimeout()` and `Promise.then()`, there are other operations that can update the data asynchronously. Some examples include `WebSocket.onmessage()` and `Canvas.toBlob()`.
The preceding list contains most common scenarios in which the application might change the data. Angular runs change detection whenever it detects that data could have changed.
The result of change detection is that DOM is updated with new data. Angular detects the changes in different ways. For component initialization, Angular calls change detection explicitly. For [asynchronous operations](https://developer.mozilla.org/en-US/docs/Learn/JavaScript/Asynchronous), Angular uses a Zone to detect changes in places where the data could have possibly mutated and it runs change detection automatically.
The result of change detection is that the DOM is updated with new data. Angular detects the changes in different ways. For component initialization, Angular calls change detection explicitly. For [asynchronous operations](https://developer.mozilla.org/en-US/docs/Learn/JavaScript/Asynchronous), Angular uses a zone to detect changes in places where the data could have possibly mutated and it runs change detection automatically.
## Zones and execution contexts
A zone provides an execution context that persists across async tasks. [Execution Context](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/this) is an abstract concept that holds information about the environment within the current code being executed. Consider the following example.
A zone provides an execution context that persists across async tasks. [Execution Context](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/this) is an abstract concept that holds information about the environment within the current code being executed. Consider the following example:
```javascript
const callback = function() {
console.log('setTimeout callback context is', this);
}
const ctx1 = {
name: 'ctx1'
};
const ctx2 = {
name: 'ctx2'
};
const ctx1 = { name: 'ctx1' };
const ctx2 = { name: 'ctx2' };
const func = function() {
console.log('caller context is', this);
@ -198,8 +194,8 @@ func.apply(ctx1);
func.apply(ctx2);
```
The value of `this` in the callback of `setTimeout` might differ depending on when `setTimeout` is called.
Thus you can lose the context in asynchronous operations.
The value of `this` in the callback of `setTimeout()` might differ depending on when `setTimeout()` is called.
Thus, you can lose the context in asynchronous operations.
A zone provides a new zone context other than `this`, the zone context that persists across asynchronous operations.
In the following example, the new zone context is called `zoneThis`.
@ -231,15 +227,15 @@ const zone = Zone.current.fork({
return delegate.scheduleTask(target, task);
},
onInvokeTask: function(delegate, curr, target, task, applyThis, applyArgs) {
console.log('task will be invoked', task.type, task.source);
console.log('task will be invoked:', task.type, task.source);
return delegate.invokeTask(target, task, applyThis, applyArgs);
},
onHasTask: function(delegate, curr, target, hasTaskState) {
console.log('task state changed in the zone', hasTaskState);
console.log('task state changed in the zone:', hasTaskState);
return delegate.hasTask(target, hasTaskState);
},
onInvoke: function(delegate, curr, target, callback, applyThis, applyArgs) {
console.log('the callback will be invoked', callback);
console.log('the callback will be invoked:', callback);
return delegate.invoke(target, callback, applyThis, applyArgs);
}
});
@ -252,43 +248,43 @@ zone.run(() => {
The above example creates a zone with several hooks.
`onXXXTask` hooks trigger when the status of Task changes.
The Zone Task concept is very similar to the Javascript VM Task concept.
- `macroTask`: such as `setTimeout()`.
- `microTask`: such as `Promise.then()`.
- `eventTask`: such as `element.addEventListener()`.
The `onXXXTask` hooks trigger when the status of the task changes.
The concept of a *Zone Task* is very similar to the JavaScript VM Task concept:
- `macroTask`: such as `setTimeout()`
- `microTask`: such as `Promise.then()`
- `eventTask`: such as `element.addEventListener()`
These hooks trigger under the following circumstances:
- `onScheduleTask`: triggers when a new asynchronous task is scheduled, such as when you call `setTimeout()`.
- `onInvokeTask`: triggers when an asynchronous task is about to execute, such as when the callback of `setTimeout()` is about to execute.
- `onHasTask`: triggers when the status of one kind of task inside a zone changes from stable to unstable or from unstable to stable. A status of stable means there are no tasks inside the Zone, while unstable means a new task is scheduled in the zone.
- `onHasTask`: triggers when the status of one kind of task inside a zone changes from stable to unstable or from unstable to stable. A status of "stable" means there are no tasks inside the zone, while "unstable" means a new task is scheduled in the zone.
- `onInvoke`: triggers when a synchronous function is going to execute in the zone.
With these hooks, `Zone` can monitor the status of all synchronous and asynchronous operations inside a zone.
The above example returns the following output.
The above example returns the following output:
```
the callback will be invoked () => {
the callback will be invoked: () => {
setTimeout(() => {
console.log('timeout callback is invoked.');
});
}
new task is scheduled: macroTask setTimeout
task state changed in the zone { microTask: false,
task state changed in the zone: { microTask: false,
macroTask: true,
eventTask: false,
change: 'macroTask' }
task will be invoked macroTask setTimeout
task will be invoked macroTask: setTimeout
timeout callback is invoked.
task state changed in the zone { microTask: false,
task state changed in the zone: { microTask: false,
macroTask: false,
eventTask: false,
change: 'macroTask' }
```
All of the functions of Zone are provided by a library called [zone.js](https://github.com/angular/angular/tree/master/packages/zone.js/README.md).
All of the functions of `Zone` are provided by a library called [Zone.js](https://github.com/angular/angular/tree/master/packages/zone.js/README.md).
This library implements those features by intercepting asynchronous APIs through monkey patching.
Monkey patching is a technique to add or modify the default behavior of a function at runtime without changing the source code.
@ -300,14 +296,14 @@ This service creates a zone named `angular` to automatically trigger change dete
1. When a sync or async function is executed.
1. When there is no `microTask` scheduled.
### NgZone `run()`/`runOutsideOfAngular()`
### NgZone `run()` and `runOutsideOfAngular()`
`Zone` handles most asynchronous APIs such as `setTimeout()`, `Promise.then()`, and `addEventListener()`.
For the full list, see the [Zone Module document](https://github.com/angular/angular/blob/master/packages/zone.js/MODULE.md).
Therefore in those asynchronous APIs, you don't need to trigger change detection manually.
There are still some third party APIs that Zone does not handle.
In those cases, the NgZone service provides a [`run()`](api/core/NgZone#run) method that allows you to execute a function inside the angular zone.
In those cases, the `NgZone` service provides a [`run()`](api/core/NgZone#run) method that allows you to execute a function inside the angular zone.
This function, and all asynchronous operations in that function, trigger change detection automatically at the correct time.
```typescript
@ -328,7 +324,7 @@ export class AppComponent implements OnInit {
By default, all asynchronous operations are inside the angular zone, which triggers change detection automatically.
Another common case is when you don't want to trigger change detection.
In that situation, you can use another NgZone method: [runOutsideAngular()](api/core/NgZone#runoutsideangular).
In that situation, you can use another `NgZone` method: [`runOutsideAngular()`](api/core/NgZone#runoutsideangular).
```typescript
export class AppComponent implements OnInit {
@ -349,7 +345,7 @@ export class AppComponent implements OnInit {
### Setting up Zone.js
To make Zone.js available in Angular, you need to import the zone.js package.
To make Zone.js available in Angular, you need to import the `zone.js` package.
If you are using the Angular CLI, this step is done automatically, and you will see the following line in the `src/polyfills.ts`:
```typescript
@ -364,17 +360,20 @@ Before importing the `zone.js` package, you can set the following configuration
- You can disable some asynchronous API monkey patching for better performance.
For example, you can disable the `requestAnimationFrame()` monkey patch, so the callback of `requestAnimationFrame()` will not trigger change detection.
This is useful if, in your application, the callback of the `requestAnimationFrame()` will not update any data.
- You can specify that certain DOM events not run inside the angular zone; for example, to prevent a `mousemove` or `scroll` event to trigger change detection.
- You can specify that certain DOM events do not run inside the angular zone; for example, to prevent a `mousemove` or `scroll` event to trigger change detection.
There are several other settings you can change.
To make these changes, you need to create a `zone-flags.ts` file, such as the following.
```typescript
(window as any).__Zone_disable_requestAnimationFrame = true; // disable patch requestAnimationFrame
(window as any).__zone_symbol__UNPATCHED_EVENTS = ['scroll', 'mousemove']; // disable patch specified eventNames
// disable patching requestAnimationFrame
(window as any).__Zone_disable_requestAnimationFrame = true;
// disable patching specified eventNames
(window as any).__zone_symbol__UNPATCHED_EVENTS = ['scroll', 'mousemove'];
```
Next, import `zone-flags` before you import `zone` in the `polyfills.ts`.
Next, import `zone-flags` before you import `zone.js` in the `polyfills.ts`:
```typescript
/***************************************************************************************************
@ -384,12 +383,12 @@ import `./zone-flags`;
import 'zone.js/dist/zone'; // Included with Angular CLI.
```
For more information of what you can configure, see the [zone.js](https://github.com/angular/angular/tree/master/packages/zone.js) documentation.
For more information about what you can configure, see the [Zone.js](https://github.com/angular/angular/tree/master/packages/zone.js) documentation.
### NoopZone
`Zone` helps Angular know when to trigger change detection and let the developers focus on the application development.
By default, `Zone` is loaded and works without additional configuration. However, you don't have to use `Zone` to make Angular work, instead opting to trigger change detection on your own.
By default, `Zone` is loaded and works without additional configuration. However, you don't necessarily have to use `Zone` to make Angular work. Instead, you can opt to trigger change detection on your own.
<div class="alert is-helpful">
@ -399,9 +398,9 @@ By default, `Zone` is loaded and works without additional configuration. However
</div>
To remove `zone.js`, make the following changes.
To remove Zone.js, make the following changes.
1. Remove the `zone.js` import from `polyfills.ts`.
1. Remove the `zone.js` import from `polyfills.ts`:
```typescript
/***************************************************************************************************
@ -410,7 +409,7 @@ To remove `zone.js`, make the following changes.
// import 'zone.js/dist/zone'; // Included with Angular CLI.
```
2. Bootstrap Angular with `noop zone` in `src/main.ts`.
2. Bootstrap Angular with the `noop` zone in `src/main.ts`:
```typescript
platformBrowserDynamic().bootstrapModule(AppModule, { ngZone: 'noop' })