AhsanAyaz

function evaluatePrice(vehicle: Vehicle) {
  switch(vehicle.vType) {
    case "car":
      return vehicle.transmission * evaluationFactor;
    case "truck":
      return vehicle.capacity * evaluationFactor;
    case "motorcycle":
      return vehicle.make * evaluationFactor;
    default:
      const invalidVehicle: never = vehicle;

AhsanAyaz

interface IBicycle {
  vType: "bicycle";
  make: number;
}
type Vehicle = IMotorcycle | ICar | ITruck | IBicycle;

AhsanAyaz

function evaluatePrice(vehicle: Vehicle) {
  switch(vehicle.vType) {
    case "car":
      return vehicle.transmission * evaluationFactor;
    case "truck":
      return vehicle.capacity * evaluationFactor;
    case "motorcycle":
      return vehicle.make * evaluationFactor;
  }
}

AhsanAyaz

const evaluationFactor = Math.PI; // some global factor
function evaluatePrice(vehicle: Vehicle) {
  return vehicle.capacity * evaluationFactor;
}
const myTruck: ITruck = {vType: "truck", capacity: 9.5};
evaluatePrice(myTruck);

AhsanAyaz

type Vehicle = IMotorcycle | ICar | ITruck;

AhsanAyaz

enum CarTransmission {
  Automatic = 200,
  Manual = 300
}

interface IMotorcycle {
  vType: "motorcycle"; // discriminant
  make: number; // year
}

AhsanAyaz

import { Injectable } from '@angular/core';
import { BehaviorSubject, Observable } from 'rxjs';

export interface LoggerConfig {
  prefix?: string;
  color?: string;
  enabled: boolean;
}

@Injectable({

AhsanAyaz

import { Component, OnInit, Input, EventEmitter, Output } from '@angular/core';

@Component({
  selector: 'app-list-item',
  templateUrl: './list-item.component.html',
  styleUrls: ['./list-item.component.scss']
})
export class ListItemComponent implements OnInit {
  @Input() item;
  @Output() itemSelected = new EventEmitter<any>();

AhsanAyaz

import { Component, OnInit, QueryList, ViewChildren } from '@angular/core';
import { UsersService } from './core/services/users.service';
import { first } from 'rxjs/operators';
import { ListKeyManager } from '@angular/cdk/a11y';
import { ListItemComponent } from './core/components/list-item/list-item.component';
import { UP_ARROW, DOWN_ARROW, ENTER } from '@angular/cdk/keycodes';


@Component({
  selector: 'app-root',

AhsanAyaz

...
import { ListKeyManager } from '@angular/cdk/a11y';
import { ListItemComponent } from './core/components/list-item/list-item.component';
import { UP_ARROW, DOWN_ARROW, ENTER } from '@angular/cdk/keycodes';

...
export class AppComponent implements OnInit {
  ...
  keyboardEventsManager: ListKeyManager<any>;
  searchQuery: string;