CODEWITHSUNDEEP
angulartypescriptdebouncingangular2-pipe
Chrillewoodz
Chrillewoodz

Reputation: 28328

Angular 2 add debounce function directly to pipe

I've written a pipe that filters out an array of objects based on a given query. It works great but what I'd like to do is add a debounce function to this pipe directly, instead of adding it to the input's keyup event, if possible.

I've been looking around for a solution but can't seem to find anything that's specific to what I'm looking for.

import {Pipe, PipeTransform} from '@angular/core';

@Pipe({
  name: 'filterBy'
})

export class FilterByPipe implements PipeTransform {

  transform(value: any, args: string[]): any[] {

    if (!args[0]) {
      return value;
    }
    else if (value) {

      return value.filter(item => {

        // TODO: Allow args[1] to be null, therefore searching in all object properties
        if ((typeof item[args[1]] === 'string' || item[args[1]] instanceof String) && (item[args[1]].toLowerCase().indexOf(args[0].toLowerCase()) !== -1)) {
          return true;
        }
      });
    }
  }
}

Any ideas on how I would implement this in this pipe?

Upvotes: 3

Views: 7374

Answers (1)

Bazinga
Bazinga

Reputation: 11204

The debounce or delay functions are async, in this case you need to return a promise or an observable from your pipe and use the async pipe. I created a simple example to show you how to do that with observable.

@Pipe({
    name: 'myfilter'
})

export class MyFilterPipe implements PipeTransform {
    transform(items, filterBy) {
      const filteredItems = items.filter(item => item.title.indexOf(filterBy.title) !== -1);
      return Observable.of(filteredItems).delay(1000);
    }
}


@Component({
  selector: 'my-app',
  template: `
    <div>
      <ul>
        <li *ngFor="let item of items | myfilter:filterBy | async">
         {{item.title}}
        </li>
      </ul>

      <input type="text" (input)="filter($event)">

    </div>
  `,
})
export class App {
  filterBy;
  constructor() {
    this.filterBy = {title: 'hello world'};
    this.items = [{title: 'hello world'}, {title: 'hello kitty'}, {title: 'foo bar'}];
  }

  filter($event) {
    this.filterBy = {title: $event.target.value}
  }
}

Plunker

Upvotes: 2

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