kepta

const isRequired = () => { throw new Error('param is required'); };

function filterEvil(array, evil = isRequired()) {
  return array.filter(item => item !== evil);   
}

AlejandroPerezMartin

import { Directive, HostListener, ElementRef } from '@angular/core';

/**
 * This directive removes focus from the selectors after clicking on them
 */
@Directive({
  selector: 'button, a' // your selectors here!
})
export class FocusRemover {
  constructor(private elRef: ElementRef) {}

demisx

Provider	Singleton	Instantiable	Configurable
Constant	Yes	No	No
Value	Yes	No	No
Service	Yes	No	No
Factory	Yes	Yes	No
Decorator	Yes	No?	No
Provider	Yes	Yes	Yes

Constant