Zone.js in Depth
@JiaLiPassion
Who am I
- Name: Jia Li
- Company: ThisDot
- Zone.js: Code Owner
- Angular: Collaborator
Agenda
- What's Zone.js
- When and why you need Zone.js
- Zone.js in Angular
What is Zone.js
A Zone is an execution context that persists across async tasks.
Created by Brian Ford inspired by Dart.
What zone.js can do
-
Provide execution context
-
Provide async task lifecycle hook
-
Provide error handler for async operations
What is execution context
execution context is an abstract concept that holds information about the environment within which the current code is being executed
Execution Context
const globalThis = this;
function testFunc() {
console.log('this in testFunc is:', this === globalThis);
}
testFunc();
Execution Context
const testObj = {
testFunc: function() {
console.log('this in testFunc is:', this);
}
};
testObj.testFunc();
const newTestFunc = testObj.testFunc;
newTestFunc();
const newObj = {};
newTestFunc.apply(newObj);
const bindObj = {};
const boundFunc = testObj.testFunc.bind(bindObj);
boundFunc();
Execution Context in JS
- When code is executed in a function, there will be a new execution context
- Determine Scope (variables and functions the function can access)
- Determine the value of `this`.
Execution context in zone.js
zone.run(function() {
// function is in the zone
// just like `this`, we have a zoneThis === zone
expect(zoneThis).toBe(zone);
setTimeout(function() {
// the callback of async operation
// will also have a zoneThis === zone
// which is the zoneContext when this async operation
// is scheduled.
expect(zoneThis).toBe(zone);
});
Promise.resolve(1).then(function() {
// all async opreations will be in the same zone
// when they are scheduled.
expect(zoneThis).toBe(zone);
});
});
Execution Context in Zone.js
- It looks like we have a new `zoneThis` magic variable like `this`.
- for sync operation, `zoneThis` will be the zone it is running in.
- for async operation, `zoneThis` will be the zone it is scheduled.
How to get `zoneThis`
zone.run(function() {
expect(Zone.current).toBe(zone);
setTimeout(function() {
expect(Zone.current).toBe(zone);
});
});
LifeCycle Interceptable Hooks
- onFork
- onIntercept
- onInvoke
- onHandleError
- onScheduleTask
- onInvokeTask
- onCancelTask
- onHasTask
setTimeout
setTimeout(function() {
console.log('callback invoked');
}, 1000);
Async in Javascript Engine
// Javascirpt 101
function a() {}
function b() {}
function c() {}
function d() {}
a();
setTimeout(c, 100);
setTimeout(d, 100);
b();
// run order
// 1. a
// 2. b
// 3. c
// 4. d
performance counter
// Javascirpt 101
function a() {// cost 100ms }
function b() {// cost 100ms }
function c() {// cost 100ms }
function d() {// cost 100ms }
performance.start();
a();
setTimeout(c, 100);
setTimeout(d, 200);
b();
performance.end();
Async in Javascript
Time
a
b
c
d
performance.start()
performance.end()
setTimeout in Zone
var zone = Zone.current.fork({
name: 'hook',
onScheduleTask: ...,
onInvokeTask: ....,
onHasTask: ...
});
zone.run(() => {
setTimeout(() => {
console.log('timer callback invoked');
}, 100);
});
Zone
zoneA = {
onInvokeTask: (callback) => {
performance.start();
callback();
performance.end();
}
};
zoneA.run(() => {
performance.start();
a();
setTimeout(c);
setTimeout(d);
b();
performance.end();
});
setTimeout(e);
Zone
Time
a
b
c
performance.start()
performance.end()
performance.start()
performance.end()
d
performance.start()
performance.end()
e
zoneA
zoneA
zoneA
zoneA
Hooks
- onScheduleTask
- onInvokeTask
- onCancelTask
- onInvoke
Async Error Handling
Zone.current.fork(
{
name: 'error',
onHandleError: (delegate, curr, target, error) => {
logger.error(error);
return delegate.handleError(target, error);
}
}).runGuarded(() => {
setTimeout(() => {
throw new Error('timeout error');
});
setTimeout(() => {
throw new Error('another timeout error');
});
});
Zone.current
console.log('root zone:', Zone.current.name);
Zone.current.fork({name: 'logZone'}).run(() => {
console.log('root zone:', Zone.current.name);
});
fork
zone.fork(zoneSpec);
interface ZoneSpec {
name: string;
onScheduleTask: ...,
onInvokeTask: ...,
onCancelTask: ...,
onInvoke: ...,
...,
}
Propagation
const stackTraceZone = Zone.current.fork({
name: 'stackTraceZone',
onScheduleTask: ...
onInvokeTask: ...
});
const logZone = stackTraceZone.fork({
name: 'logZone',
onInvokeTask: ...
});
logZone.run(() => {
setTimeout(...)
});
Propagation
rootZone
stackTraceZone
logZone
onInvokeTask
onInvokeTask
Zone propagation can compose zone behaviors
Zone.wrap
function testFunc() {
console.log('this in testFunc is:', this);
}
const bindTarget = {};
const boundFunc = testFunc.bind(bindTarget);
boundFunc.apply(newObj);
// ------------------------
//
function testZoneFunc() {
console.log('zoneThis in testFunc is:', Zone.current);
}
const zoneA = Zone.current.fork({name: 'zoneA'});
const wrappedTestZoneFunc = zoneA.wrap(testZoneFunc);
zoneB.run(wrappedTestZoneFunc);
Task
- macroTask
- setTimeout
- setInterval
- XHR
- ...
- microTask
- Promise.then
- eventTask
- addEventListener
- on('event', fn)
zone.scheduleMicrotask
zone.scheduleMicroTask('myOwnMicroTask', callbackFn);
// looks like
Promise.resolve().then(() => {
callbackFn();
});
other methods
Zone.__symbol__ // will return a string starts with __symbol__
Zone.__symbol__('test') === '__zone_symbol__test';
Zone.__load_patch('myOwnAsyncApi',
(global, Zone, api) => {});
Monkey-Patch
const api = {
add: function add(a, b) {
return a + b;
}
}
api.add(1, 2); // will return 3;
const originalAdd = api.add;
api.add = function() {
console.log('api.add is called');
return originalAdd.apply(this, arguments);
}
api.add(1, 2); // will log and return 3;
When should we use Zone
- Test
- Sync(Disallow Async)
- Async(Auto done, Auto cleanup)
- FakeAsync()
- Debug
- LongStackTrace
- Task Tracing
- Performance measure
- Framework AutoRender
- User Action Tracing
- Resource Releasing
Demo: LongStackTrace
function main () {
b1.addEventListener('click', bindSecondButton);
}
/*
* What if your stack trace could tell you what
* order the user pushed the buttons from the stack trace?
* What if you could log this back to the server?
* Think of how much more productive your debugging could be!
*/
function bindSecondButton () {
b2.addEventListener('click', throwError);
}
function throwError () {
throw new Error('aw shucks');
}
main();
Demo: Tracking: Counting
function btnClicked () {
recurRandonGenerateTimeout(10);
}
function recurRandonGenerateTimeout (x) {
if (x > 0) {
setTimeout(function () {
for (var i = x; i < 8; i++) {
recur(x - 1, Math.random()*100);
}
}, t);
}
}
Performance Profiling
function btnClicked () {
asyncHeavyWork1();
asyncHeavyWork2();
asyncHttpRequest();
}
Auto releasing
const fs = require('fs');
fs.open('./test.txt', 'r', (err, fd) => {
if (err) throw err;
fs.fstat(fd, (err, stat) => {
if (err) throw err;
doSomething(fd, err => {});
doSomethingElse(fd, err => {});
});
});
User Action Tracking
viewBtnClicked() {
httpRequest(viewUrl);
httpRequest(additionalInfoUrl);
}
orderBtnClicked() {
httpRequest(orderUrl);
httpRequest(transactionUrl);
}
errorBtnClicked() {
throw new Error();
}
UI Auto Rendering
function httpBtnClicked() {
httpRequestUrl(viewUrl);
}
function timeoutBtnClicked() {
setTimeout(() => {
data.timeout = 'timeout';
});
}
function addBtnClicked() {
if (!data.num) {
data.num = 0;
}
data.num ++;
}
Async Test
const api = require('./async-lib');
describe('testAsync', () => {
it('test async operation', (done) => {
let a = 0;
api.testAsync(a, r => {
expect(r).toBe(1);
done();
});
});
});
const api = require('./async-lib');
describe('testAsync', async(() => {
it('test async operation', () => {
let a = 0;
api.testAsync(a, r => {
expect(r).toBe(1);
});
});
}));
fakeAsync Test
describe('testAsync', () => {
it('test long async operation', (done) => {
setTimeout(() => {
// ... expect something.
done();
}, 10000);
});
});
describe('testAsync', () => {
it('test long async operation', fakeAsync(() => {
setTimeout(() => {
// ... expect something.
}, 10000);
tick(10000);
}));
});
Zone.js in Angular
NgZone
Tell when to trigger Change Detection
AsyncTest
FakeAsyncTest
SyncTest
Error Handling
Debug/Tracing
TaskTrackingZone
LongStackTraceZone
ngZone
ngZone.run(() => {
// will be in angular zone
// will trigger change detection
});
ngZone.runOutsideAngular(() => {
// will be outside angular zone
// will not trigger change detection
});
Features of zone.js you may not know
Module
Timer
Promise
EventTarget
...
requestAnimationFrame
Disable specified Module
(window as any).__Zone_disable_requestAnimationFrame = true;
Ionic v4
(window as any).__Zone_disable_customElements = true;
Disable Specified Event
// recommended variable name
__zone_symbol__UNPATCHED_EVENTS = ['scroll', 'mousemove'];
// deprecated variable name
// __zone_symbol__BLACK_LISTED_EVENTS = ['scroll', 'mousemove'];
Native Delegate
// ngZone.runOutsideAngular(() => {});
declare let Zone: any;
(window as any)[Zone.__symbol__('setTimeout')](() => {
// will not in zone.
}, 100);
Promise
ZoneAwarePromise
- Pass Promise A+ Test
- Support Promise.prototype.finally
- Support Bluebird
- All Bluebird specified APIs will in zone
- Will support Promise.any and Promise.allSettled
Error Handling
import 'zone.js/dist/zone-error';
Error Handling
import 'zone.js/dist/zone-error';
class MyError extends Error {
}
try {
throw new MyError('myError');
} catch (error: Error) {
if (error instanceof MyError) {
// do some special error handling
}
}
(window as any).__Zone_Error_BlacklistedStackFrames_policy
= 'disable';
Electron
- Browser
- NodeJs
- Menu
- Screenshot
- Shell
- Main<->Render communication
import 'zone.js/dist/zone-mix';
import 'zone.js/dist/zone-patch-electron';
More APIs Support
-
MediaQuery
-
Notification
-
RTCPeerConnction
-
ShadyDom
-
Cordova
-
ResizeObserver
-
SocketIO
-
UserMedia
-
Jsonp Helper
FakeAsync: Date.now
will support performance api later
it('should advance Date with tick in fakeAsync',
fakeAsync(() => {
const start = Date.now();
tick(100);
const end = Date.now();
expect(end - start).toBe(100);
}));
FakeAsync: jasmine.clock
beforeEach(() => {
jasmine.clock().install();
});
afterEach(() => {
jasmine.clock().uninstall();
});
it('should get date diff correctly', () => {
// automatically run into fake async zone,
const start = Date.now();
jasmine.clock().tick(100);
const end = Date.now();
expect(end - start).toBe(100);
});
__zone_symbol__fakeAsyncAutoFakeAsyncWhenClockPatched
FakeAsync: rxjs.scheduler
import 'zone.js/dist/zone-patch-rxjs-fake-async';
it('rxjs scheduler should be advanced by tick in fakeAsync',
fakeAsync(() => {
observable.delay(1000).subscribe(v => {
result = v;
});
expect(result).toBeNull();
testZoneSpec.tick(1000);
expect(result).toBe('hello');
}));
Better timeout message
it('should timeout', async(() => {
setTimeout(() => {}, 10000);
fixture.whenStable(() => {});
}));
Error: Timeout - Async callback was not invoked within timeout specified by jasmine.DEFAULT_TIMEOUT_INTERVAL.
--Pendng async tasks are: [type: macroTask, source: setTimeout, args: {handleId:3,isPeriodic:false,delay:10000,args:[]}
Jasmine 3.x/Mocha 5.x
Will support Jest!
- Better error message
- Better jest timer(useFakeTimers/runAllTicks/etc...) support
Differential Loading
<script src="zone.js/dist/zone-evergreen.js"
type="module"></script>
<script src="zone.js/dist/zone.js" nomodule></script>
Event Bubble Performance
<div (click)="doSomethingElse()">
<button (click)="doSomething()">click me</button>
</div>
platformBrowserDynamic()
.bootstrapModule(
AppModule,
{
ngZoneEventCoalescing: true
}
)
Solution
Event Listeners
button.addEventListener('click', click1);
button.addEventListener('click', click2);
button.addEventListener('mousedown', mousedown1);
const clickListeners = button.eventListeners('click');
// will get click1 and click2
button.removeAllListeners('click');
// will remove click1 and click2
button.removeAllListeners();
// will remove all listeners for all events
Zone.js is merged into angular mono repo !!!
Thank you!
Zone.js in depth
By jiali
Zone.js in depth
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