Angular4: How am I * ngFor, for each number in int?

Question

I have an int property called "count" in my component.

I would like to display the p-tag of X the number of times where X is the value of int my count. Is there really no easy way to do this other than bothering with fake arrays?

Answer 1

Plnkr: https://plnkr.co/edit/Yn775KSbBeUPeyaI9sep?p=preview

You can create another variable called countObservable

  countObservable = Observable.range(0, this.count).toArray();

Use async for HTML

  <p *ngFor="let num of countObservable | async" >Hello {{num}}</h2>

Refresh

If we need to update the number, we can use flatMap.

Instead of the above code for countObservable use this

count$= new BehaviorSubject(10);
countObservable$ = 
  this.count$.flatMap(count => Observable.range(0, count).toArray()) ;

, count$

this.count$.next(newNum);

Answer 2

, param = number.

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

@Pipe({  
    name: 'range',  
    pure: false  
})  

export class RangePipe implements PipeTransform {  
    transform(items: any[], quantity: number): any {  
      items.length = 0;
      for (let i = 0; i < quantity; i++) {
        items.push(i);
      }
      return items;
    }  
}  

<div *ngFor="let n of [] | range:100"></div>

Answer 3

n , n , :

import { Directive, Input, TemplateRef, ViewContainerRef, isDevMode, EmbeddedViewRef } from '@angular/core';

export class ForNumberContext {
  constructor(public count: number, public index: number) { }
  get first(): boolean { return this.index === 0; }

  get last(): boolean { return this.index === this.count - 1; }

  get even(): boolean { return this.index % 2 === 0; }

  get odd(): boolean { return !this.even; }
}

@Directive({
  selector: '[ForNumber]'
})
export class ForNumberDirective {


 @Input() set forNumberOf(n: number) {
    this._forNumberOf = n;
    this.generate();
  }

  private _forNumberOf: number;

  constructor(private _template: TemplateRef<ForNumberContext>,
    private _viewContainer: ViewContainerRef) { }

  @Input()
  set ngForTemplate(value: TemplateRef<ForNumberContext>) {
    if (value) {
      this._template = value;
    }
  }

  private generate() {
    for (let i = 0; i < this._forNumberOf; i++) {
      this._viewContainer.createEmbeddedView(this._template, new ForNumberContext(this._forNumberOf, i));
    }
  }

}

:

<ng-template ForNumber [forNumberOf]="count" let-index="index">
<span>Iteration: {{index}}!</span></ng-template>

, , , :)