Angular 2+和debounce

在AngularJS中，我可以使用ng-model选项来撤销一个模型。

ng-model-options="{ debounce: 1000 }"

如何在Angular中释放一个模型? 我试着在文档里搜索debounce，但什么都没找到。

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);

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中有吗?

当前回答

你可以创建一个RxJS (v.6) Observable来做任何你想做的事情。

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);
  }  


}

2017-05-16 05:11:54

其他回答

简单的解决方法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);
                }
            });
    }
}

用法是

<textarea [ngModel]="somevalue"   
          [debounce]="2000"
          (onDebounce)="somevalue = $event"                               
          rows="3">
</textarea>

2017-02-02 22:32:16

它可以作为指令来执行

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();
  }

}

像这样使用它

<input [(ngModel)]="value" (onDebounce)="doSomethingWhenModelIsChanged($event)">

组件示例

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);
    });
  }
}

2017-02-10 12:37:39

你可以创建一个RxJS (v.6) Observable来做任何你想做的事情。

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);
  }  


}

2017-05-16 05:11:54

花了好几个小时在这上面，希望我能帮别人省点时间。对我来说，下面的方法对一个控件使用debounce更直观，更容易理解。它是建立在角上的。io文档解决方案的自动完成，但有能力为我拦截调用，而不必依赖于绑定数据到DOM。

砰砰作响

这种情况的一个用例场景可能是在输入用户名后检查用户名，看看是否有人已经使用了它，然后警告用户。

注意:不要忘记，(blur)="function(something.value)可能更适合你，这取决于你的需要。

2016-09-22 19:51:15

你也可以通过使用装饰器来解决这个问题，例如通过使用utils-decorator lib中的debounce装饰器(npm install utils-decorators):

import {debounce} from 'utils-decorators';

class MyAppComponent {

  @debounce(500)
  firstNameChanged($event, first) {
   ...
  }
}

2020-04-12 20:41:05

Angular 2+和debounce

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