Monkey patching Angular's ngFor to allow "let item in items" instead of "let items of items"

ng_for_in---same_as_for_of.ts

/*
 * This directive simply allows to use "let item in items" instead of "let item of items"
 * with ngFor. Its functionality remains unchanged (that is, it still loops over the iterable's values)
 * 
 * To use it just import it into your module and add it to its "declarations".
 */

import {
  Directive, TemplateRef, Input, ChangeDetectorRef, ViewContainerRef,
  IterableDiffers, OnChanges, SimpleChanges
} from '@angular/core';
import { NgFor } from "@angular/common";
import { NgForRow } from "@angular/common/src/directives/ng_for";

@Directive({selector: '[ngFor][ngForIn]'})
export class NgForIn extends NgFor implements OnChanges {
  @Input() ngForIn: any;

  constructor(viewContainer: ViewContainerRef,
              template: TemplateRef<NgForRow>,
              differs: IterableDiffers,
              cdr: ChangeDetectorRef) {

    super(viewContainer, template, differs, cdr);
  }

  ngOnChanges(changes: SimpleChanges): void {
    if ('ngForIn' in changes) {
      this.ngForOf = this.ngForIn;
      changes['ngForOf'] = changes['ngForIn'];
      super.ngOnChanges(changes);
    }
  }
}