ngrx-action-debouncer

Debounce a stream of actions before being dispatched to @ngrx/store.

This library is designed to work with @ngrx/store apps written with Angular v5+.

Get the Changelog.

API

The library provides an injectable NgrxActionDebouncerService with a single debounceAction method.

public debounceAction <A extends Action>(action: A, dueTime: number = 0): void {
  ...
}

How it works

Consider an application where a user enters text in an input, and receives search results in return. An implementation using @ngrx/store might result in the following actions being dispatched over time as a result of the user typing "ang".

// 0ms
this.store.dispatch({
  type: 'SEARCH_ACTION',
  payload: 'a'
});

...

// 50ms after initial action
this.store.dispatch({
  type: 'SEARCH_ACTION',
  payload: 'an'
});

...

// 80ms after initial action
this.store.dispatch({
  type: 'SEARCH_ACTION',
  payload: 'ang'
});

ngrx-action-debouncer would view all of the above actions as belonging to the same stream of actions because their type is identical. Using debounceAction() with a due time of 75ms would result in only one of the three actions being dispatched to the store:

// 0ms
//
// action is 'debounced' & not dispatched to the store
this.debouncer.debounceAction({
  type: 'SEARCH_ACTION',
  payload: 'a'
}, 75);

...

// 50ms after initial action
//
// action is 'debounced' & not dispatched to the store
this.debouncer.debounceAction({
  type: 'SEARCH_ACTION',
  payload: 'an'
}, 75);

...

// 80ms after initial action
//
// action IS dispatched to the store a total of 155ms after
// the initial action
this.debouncer.debounceAction({
  type: 'SEARCH_ACTION',
  payload: 'ang'
}, 75);

Multiple Types of Actions

debounceAction() can safely be used with multiple types of actions. See the library's unit tests for an example of why this works.

Usage

Import NgrxActionDebouncerModule only once, into your app's root module:

// app.module.ts

import { NgrxActionDebouncerModule } from 'ngrx-action-debouncer';

@NgModule({
  declarations: [
    AppComponent,
    SampleComponent
  ],
  imports: [
    BrowserModule,
    StoreModule.forRoot(reducers),
    NgrxActionDebouncerModule
  ],
  providers: [],
  bootstrap: [
    AppComponent
  ]
})
export class AppModule { }

Inject NgrxActionDebouncerService into Components, Services, etc. as needed:

import { Component } from '@angular/core';

import { NgrxActionDebouncerService } from 'ngrx-action-debouncer';

@Component({
  selector: 'app-sample',
  template: `
    <button type="button" (click)="onClick()">
      Increment
    </button>
  `
})
export class SampleComponent {
  constructor (private debouncer: NgrxActionDebouncerService) { }

  onClick () {
    const action = {
      type: 'INCREMENT'
    };

    // 500ms
    const dueTime = 500;

    this.debouncer.debounceAction(action, dueTime);
  }
}

Installation, Loading & Compilation

Installing

npm install ngrx-action-debouncer --save

Loading

Using SystemJS configuration

System.config({
  map: {
    'ngrx-action-debouncer': 'node_modules/ngrx-action-debouncer/bundles/ngrx-action-debouncer.umd.js'
  }
});

AoT compilation

The library is compatible with AoT compilation.

License

MIT