在 AngularJS 中,我可以通过使用 ng-model 选项来消除模型的抖动。
ng-model-options="{ debounce: 1000 }"
如何在 Angular 中消除模型的抖动?我试图在文档中搜索去抖动,但我找不到任何东西。
https://angular.io/search/#stq=debounce&stp=1
一个解决方案是编写我自己的 debounce 函数,例如:
import {Component, Template, bootstrap} from 'angular2/angular2';
// Annotation section
@Component({
selector: 'my-app'
})
@Template({
url: 'app.html'
})
// Component controller
class MyAppComponent {
constructor() {
this.firstName = 'Name';
}
changed($event, el){
console.log("changes", this.name, el.value);
this.name = el.value;
}
firstNameChanged($event, first){
if (this.timeoutId) window.clearTimeout(this.timeoutID);
this.timeoutID = window.setTimeout(() => {
this.firstName = first.value;
}, 250)
}
}
bootstrap(MyAppComponent);
还有我的html
<input type=text [value]="firstName" #first (keyup)="firstNameChanged($event, first)">
但我正在寻找一个内置函数,Angular中有一个吗?
更新为 RC.5
使用 Angular 2,我们可以在表单控件的 valueChanges
observable 上使用 RxJS 运算符 debounceTime()
去抖动:
import {Component} from '@angular/core';
import {FormControl} from '@angular/forms';
import {Observable} from 'rxjs/Observable';
import 'rxjs/add/operator/debounceTime';
import 'rxjs/add/operator/throttleTime';
import 'rxjs/add/observable/fromEvent';
@Component({
selector: 'my-app',
template: `<input type=text [value]="firstName" [formControl]="firstNameControl">
<br>{{firstName}}`
})
export class AppComponent {
firstName = 'Name';
firstNameControl = new FormControl();
formCtrlSub: Subscription;
resizeSub: Subscription;
ngOnInit() {
// debounce keystroke events
this.formCtrlSub = this.firstNameControl.valueChanges
.debounceTime(1000)
.subscribe(newValue => this.firstName = newValue);
// throttle resize events
this.resizeSub = Observable.fromEvent(window, 'resize')
.throttleTime(200)
.subscribe(e => {
console.log('resize event', e);
this.firstName += '*'; // change something to show it worked
});
}
ngDoCheck() { console.log('change detection'); }
ngOnDestroy() {
this.formCtrlSub.unsubscribe();
this.resizeSub .unsubscribe();
}
}
上面的代码还包括一个如何限制窗口调整大小事件的示例,正如@albanx 在下面的评论中所要求的那样。
尽管上面的代码可能是 Angular 的做法,但效率不高。每次击键和每次调整大小事件,即使它们被去抖动和限制,都会导致更改检测运行。换言之,去抖动和限制不会影响更改检测的运行频率。 (我发现 Tobias Bosch 的 GitHub comment 证实了这一点。)您可以在运行 plunker 时看到这一点,并且您会看到在输入框或调整窗口大小时调用了多少次 ngDoCheck()
。 (使用蓝色的“x”按钮在单独的窗口中运行 plunker 以查看调整大小事件。)
一种更有效的技术是自己从事件中创建 RxJS Observables,在 Angular 的“区域”之外。这样,每次触发事件时都不会调用更改检测。然后,在您的订阅回调方法中,手动触发更改检测——即,您控制何时调用更改检测:
import {Component, NgZone, ChangeDetectorRef, ApplicationRef,
ViewChild, ElementRef} from '@angular/core';
import {Observable} from 'rxjs/Observable';
import 'rxjs/add/operator/debounceTime';
import 'rxjs/add/operator/throttleTime';
import 'rxjs/add/observable/fromEvent';
@Component({
selector: 'my-app',
template: `<input #input type=text [value]="firstName">
<br>{{firstName}}`
})
export class AppComponent {
firstName = 'Name';
keyupSub: Subscription;
resizeSub: Subscription;
@ViewChild('input') inputElRef: ElementRef;
constructor(private ngzone: NgZone, private cdref: ChangeDetectorRef,
private appref: ApplicationRef) {}
ngAfterViewInit() {
this.ngzone.runOutsideAngular( () => {
this.keyupSub = Observable.fromEvent(this.inputElRef.nativeElement, 'keyup')
.debounceTime(1000)
.subscribe(keyboardEvent => {
this.firstName = keyboardEvent.target.value;
this.cdref.detectChanges();
});
this.resizeSub = Observable.fromEvent(window, 'resize')
.throttleTime(200)
.subscribe(e => {
console.log('resize event', e);
this.firstName += '*'; // change something to show it worked
this.cdref.detectChanges();
});
});
}
ngDoCheck() { console.log('cd'); }
ngOnDestroy() {
this.keyupSub .unsubscribe();
this.resizeSub.unsubscribe();
}
}
我使用 ngAfterViewInit()
而不是 ngOnInit()
来确保定义了 inputElRef
。
detectChanges()
将对此组件及其子组件运行更改检测。如果您希望从根组件运行更改检测(即运行完整的更改检测检查),请改用 ApplicationRef.tick()
。 (我在 plunker 的评论中调用了 ApplicationRef.tick()
。)请注意,调用 tick()
将导致调用 ngDoCheck()
。
如果您不想处理 @angular/forms
,您可以使用带有更改绑定的 RxJS Subject
。
view.component.html
<input [ngModel]='model' (ngModelChange)='changed($event)' />
view.component.ts
import { Subject } from 'rxjs';
import { Component } from '@angular/core';
import 'rxjs/add/operator/debounceTime';
export class ViewComponent {
model: string;
modelChanged: Subject<string> = new Subject<string>();
constructor() {
this.modelChanged
.debounceTime(300) // wait 300ms after the last event before emitting last event
.distinctUntilChanged() // only emit if value is different from previous value
.subscribe(model => this.model = model);
}
changed(text: string) {
this.modelChanged.next(text);
}
}
这确实会触发更改检测。 For a way that doesn't trigger change detection, check out Mark's answer.
更新
rxjs 6 需要 .pipe(debounceTime(300), distinctUntilChanged())
。
例子:
constructor() {
this.modelChanged.pipe(
debounceTime(300),
distinctUntilChanged())
.subscribe(model => this.model = model);
}
.pipe(debounceTime(300), distinctUntilChanged())
由于该主题很旧,因此大多数答案不适用于 Angular 6-13 和/或使用其他库。因此,这里有一个使用 RxJS 的 Angular 6+ 的简短解决方案。
首先导入必要的东西:
import { Component, OnInit, OnDestroy } from '@angular/core';
import { Subject, Subscription } from 'rxjs';
import { debounceTime, distinctUntilChanged } from 'rxjs/operators';
实现 ngOnInit
和 ngOnDestroy
:
export class MyComponent implements OnInit, OnDestroy {
public notesText: string;
public notesModelChanged: Subject<string> = new Subject<string>();
private notesModelChangeSubscription: Subscription
constructor() { }
ngOnInit() {
this.notesModelChangeSubscription = this.notesModelChanged
.pipe(
debounceTime(2000),
distinctUntilChanged()
)
.subscribe(newText => {
this.notesText = newText;
console.log(newText);
});
}
ngOnDestroy() {
this.notesModelChangeSubscription.unsubscribe();
}
}
使用这种方式:
<input [ngModel]='notesText' (ngModelChange)='notesModelChanged.next($event)' />
PS 对于更复杂和有效的解决方案,您可能仍需要检查其他答案。
它可以作为指令实施
import { Directive, Input, Output, EventEmitter, OnInit, OnDestroy } from '@angular/core';
import { NgControl } from '@angular/forms';
import 'rxjs/add/operator/debounceTime';
import 'rxjs/add/operator/distinctUntilChanged';
import { Subscription } from 'rxjs';
@Directive({
selector: '[ngModel][onDebounce]',
})
export class DebounceDirective implements OnInit, OnDestroy {
@Output()
public onDebounce = new EventEmitter<any>();
@Input('debounce')
public debounceTime: number = 300;
private isFirstChange: boolean = true;
private subscription: Subscription;
constructor(public model: NgControl) {
}
ngOnInit() {
this.subscription =
this.model.valueChanges
.debounceTime(this.debounceTime)
.distinctUntilChanged()
.subscribe(modelValue => {
if (this.isFirstChange) {
this.isFirstChange = false;
} else {
this.onDebounce.emit(modelValue);
}
});
}
ngOnDestroy() {
this.subscription.unsubscribe();
}
}
像使用它一样
<input [(ngModel)]="value" (onDebounce)="doSomethingWhenModelIsChanged($event)">
组件样本
import { Component } from "@angular/core";
@Component({
selector: 'app-sample',
template: `
<input[(ngModel)]="value" (onDebounce)="doSomethingWhenModelIsChanged($event)">
<input[(ngModel)]="value" (onDebounce)="asyncDoSomethingWhenModelIsChanged($event)">
`
})
export class SampleComponent {
value: string;
doSomethingWhenModelIsChanged(value: string): void {
console.log({ value });
}
async asyncDoSomethingWhenModelIsChanged(value: string): Promise<void> {
return new Promise<void>(resolve => {
setTimeout(() => {
console.log('async', { value });
resolve();
}, 1000);
});
}
}
import 'rxjs/add/operator/debounceTime'; import 'rxjs/add/operator/distinctUntilChanged';
到 import { debounceTime, distinctUntilChanged } from 'rxjs/operators';
和 this.model.valueChanges .debounceTime(this.debounceTime) .distinctUntilChanged()
到 this.model.valueChanges .pipe( debounceTime(this.debounceTime), distinctUntilChanged() )
不能像 angular1 那样直接访问,但您可以轻松地使用 NgFormControl 和 RxJS 可观察对象:
<input type="text" [ngFormControl]="term"/>
this.items = this.term.valueChanges
.debounceTime(400)
.distinctUntilChanged()
.switchMap(term => this.wikipediaService.search(term));
这篇博文清楚地解释了这一点:http://blog.thoughtram.io/angular/2016/01/06/taking-advantage-of-observables-in-angular2.html
这是一个自动完成,但它适用于所有场景。
[...]
是单向目标绑定。为什么可以通知容器 valueChanges
?它不应该是某事。像(ngFormControl)="..."
?
您可以创建一个 RxJS (v.6) Observable 来做任何您喜欢的事情。
view.component.html
<input type="text" (input)="onSearchChange($event.target.value)" />
view.component.ts
import { Observable } from 'rxjs';
import { debounceTime, distinctUntilChanged } from 'rxjs/operators';
export class ViewComponent {
searchChangeObserver;
onSearchChange(searchValue: string) {
if (!this.searchChangeObserver) {
new Observable(observer => {
this.searchChangeObserver = observer;
}).pipe(debounceTime(300)) // wait 300ms after the last event before emitting last event
.pipe(distinctUntilChanged()) // only emit if value is different from previous value
.subscribe(console.log);
}
this.searchChangeObserver.next(searchValue);
}
}
rsjs/Rx
,我在使用你编写的导入方式时遇到了错误......所以在我的情况下它现在是:import { Observable } from 'rxjs/Rx';
import { Observable } from 'rxjs';
。
pipe
调用 pipe(debounceTime(300), distinctUntilChanged())
对于使用 lodash 的任何人,debounce 任何功能都非常容易:
changed = _.debounce(function() {
console.log("name changed!");
}, 400);
然后把这样的东西扔到你的模板中:
<(input)="changed($event.target.value)" />
直接在事件函数中初始化订阅者的解决方案:
import {Subject} from 'rxjs';
import {debounceTime, distinctUntilChanged} from 'rxjs/operators';
class MyAppComponent {
searchTermChanged: Subject<string> = new Subject<string>();
constructor() {
}
onFind(event: any) {
if (this.searchTermChanged.observers.length === 0) {
this.searchTermChanged.pipe(debounceTime(1000), distinctUntilChanged())
.subscribe(term => {
// your code here
console.log(term);
});
}
this.searchTermChanged.next(event);
}
}
和html:
<input type="text" (input)="onFind($event.target.value)">
我通过编写一个去抖动装饰器解决了这个问题。所描述的问题可以通过将 @debounceAccessor 应用于属性的 set 访问器来解决。
我还为方法提供了一个额外的 debounce 装饰器,这对其他场合很有用。
这使得去抖动属性或方法变得非常容易。该参数是去抖动应该持续的毫秒数,在下面的示例中为 100 毫秒。
@debounceAccessor(100)
set myProperty(value) {
this._myProperty = value;
}
@debounceMethod(100)
myMethod (a, b, c) {
let d = a + b + c;
return d;
}
这是装饰器的代码:
function debounceMethod(ms: number, applyAfterDebounceDelay = false) {
let timeoutId;
return function (target: Object, propName: string, descriptor: TypedPropertyDescriptor<any>) {
let originalMethod = descriptor.value;
descriptor.value = function (...args: any[]) {
if (timeoutId) return;
timeoutId = window.setTimeout(() => {
if (applyAfterDebounceDelay) {
originalMethod.apply(this, args);
}
timeoutId = null;
}, ms);
if (!applyAfterDebounceDelay) {
return originalMethod.apply(this, args);
}
}
}
}
function debounceAccessor (ms: number) {
let timeoutId;
return function (target: Object, propName: string, descriptor: TypedPropertyDescriptor<any>) {
let originalSetter = descriptor.set;
descriptor.set = function (...args: any[]) {
if (timeoutId) return;
timeoutId = window.setTimeout(() => {
timeoutId = null;
}, ms);
return originalSetter.apply(this, args);
}
}
}
我为方法装饰器添加了一个附加参数,让您在去抖动延迟之后触发方法。我这样做是为了例如在与 mouseover 或 resize 事件结合使用时使用它,我希望捕获发生在事件流的末尾。但是,在这种情况下,该方法不会返回值。
我们可以创建一个 [debounce] 指令,它用一个空的覆盖 ngModel 的默认 viewToModelUpdate 函数。
指令代码
@Directive({ selector: '[debounce]' })
export class MyDebounce implements OnInit {
@Input() delay: number = 300;
constructor(private elementRef: ElementRef, private model: NgModel) {
}
ngOnInit(): void {
const eventStream = Observable.fromEvent(this.elementRef.nativeElement, 'keyup')
.map(() => {
return this.model.value;
})
.debounceTime(this.delay);
this.model.viewToModelUpdate = () => {};
eventStream.subscribe(input => {
this.model.viewModel = input;
this.model.update.emit(input);
});
}
}
如何使用它
<div class="ui input">
<input debounce [delay]=500 [(ngModel)]="myData" type="text">
</div>
HTML 文件:
<input [ngModel]="filterValue"
(ngModelChange)="filterValue = $event ; search($event)"
placeholder="Search..."/>
TS 文件:
timer = null;
time = 250;
search(searchStr : string) : void {
clearTimeout(this.timer);
this.timer = setTimeout(()=>{
console.log(searchStr);
}, time)
}
Angular 7 中的 DebounceTime 与 RxJS v6
来源Link
演示Link
https://i.stack.imgur.com/zUVvj.gif
在 HTML 模板中
<input type="text" #movieSearchInput class="form-control"
placeholder="Type any movie name" [(ngModel)]="searchTermModel" />
在组件中
....
....
export class AppComponent implements OnInit {
@ViewChild('movieSearchInput') movieSearchInput: ElementRef;
apiResponse:any;
isSearching:boolean;
constructor(
private httpClient: HttpClient
) {
this.isSearching = false;
this.apiResponse = [];
}
ngOnInit() {
fromEvent(this.movieSearchInput.nativeElement, 'keyup').pipe(
// get value
map((event: any) => {
return event.target.value;
})
// if character length greater then 2
,filter(res => res.length > 2)
// Time in milliseconds between key events
,debounceTime(1000)
// If previous query is diffent from current
,distinctUntilChanged()
// subscription for response
).subscribe((text: string) => {
this.isSearching = true;
this.searchGetCall(text).subscribe((res)=>{
console.log('res',res);
this.isSearching = false;
this.apiResponse = res;
},(err)=>{
this.isSearching = false;
console.log('error',err);
});
});
}
searchGetCall(term: string) {
if (term === '') {
return of([]);
}
return this.httpClient.get('http://www.omdbapi.com/?s=' + term + '&apikey=' + APIKEY,{params: PARAMS.set('search', term)});
}
}
您也可以通过使用装饰器来解决此问题,例如使用 utils-decorator lib (npm install utils-decorators
) 中的 debounce 装饰器:
import {debounce} from 'utils-decorators';
class MyAppComponent {
@debounce(500)
firstNameChanged($event, first) {
...
}
}
简单的解决方案是创建一个可以应用于任何控件的指令。
import { Directive, ElementRef, Input, Renderer, HostListener, Output, EventEmitter } from '@angular/core';
import { NgControl } from '@angular/forms';
@Directive({
selector: '[ngModel][debounce]',
})
export class Debounce
{
@Output() public onDebounce = new EventEmitter<any>();
@Input('debounce') public debounceTime: number = 500;
private modelValue = null;
constructor(public model: NgControl, el: ElementRef, renderer: Renderer){
}
ngOnInit(){
this.modelValue = this.model.value;
if (!this.modelValue){
var firstChangeSubs = this.model.valueChanges.subscribe(v =>{
this.modelValue = v;
firstChangeSubs.unsubscribe()
});
}
this.model.valueChanges
.debounceTime(this.debounceTime)
.distinctUntilChanged()
.subscribe(mv => {
if (this.modelValue != mv){
this.modelValue = mv;
this.onDebounce.emit(mv);
}
});
}
}
用法将是
<textarea [ngModel]="somevalue"
[debounce]="2000"
(onDebounce)="somevalue = $event"
rows="3">
</textarea>
Angular 7
中编译。
花了几个小时,希望我可以节省别人一些时间。对我来说,在控件上使用 debounce
的以下方法对我来说更直观且更易于理解。它建立在用于自动完成的 angular.io docs 解决方案之上,但我能够拦截调用,而不必依赖将数据绑定到 DOM。
一个用例场景可能是在输入用户名后检查用户名以查看是否有人已经使用它,然后警告用户。
注意:不要忘记,根据您的需要,(blur)="function(something.value)
可能对您更有意义。
这是迄今为止我找到的最好的解决方案。更新 blur
和 debounce
上的 ngModel
import { Directive, Input, Output, EventEmitter,ElementRef } from '@angular/core';
import { NgControl, NgModel } from '@angular/forms';
import 'rxjs/add/operator/debounceTime';
import 'rxjs/add/operator/distinctUntilChanged';
import { Observable } from 'rxjs/Observable';
import 'rxjs/add/observable/fromEvent';
import 'rxjs/add/operator/map';
@Directive({
selector: '[ngModel][debounce]',
})
export class DebounceDirective {
@Output()
public onDebounce = new EventEmitter<any>();
@Input('debounce')
public debounceTime: number = 500;
private isFirstChange: boolean = true;
constructor(private elementRef: ElementRef, private model: NgModel) {
}
ngOnInit() {
const eventStream = Observable.fromEvent(this.elementRef.nativeElement, 'keyup')
.map(() => {
return this.model.value;
})
.debounceTime(this.debounceTime);
this.model.viewToModelUpdate = () => {};
eventStream.subscribe(input => {
this.model.viewModel = input;
this.model.update.emit(input);
});
}
}
从 https://stackoverflow.com/a/47823960/3955513 借来的
然后在 HTML 中:
<input [(ngModel)]="hero.name"
[debounce]="3000"
(blur)="hero.name = $event.target.value"
(ngModelChange)="onChange()"
placeholder="name">
在 blur
上,模型使用纯 javascript 显式更新。
此处示例:https://stackblitz.com/edit/ng2-debounce-working
.fromEvent()