Using Generics in Typescript

generics.ts

class ArrayOfNumbers {
  constructor(public collection: number[]) {}
  get(index: number): number {
    return this.collection[index];
  }
}

class ArrayOfStrings {
  constructor(public collection: string[]) {}
  get(index: number): string {
    return this.collection[index];
  }
}

class ArrayOfAnything<T> {
  constructor(public collection: T[]) {}

  get(index: number): T {
    return this.collection[index];
  }
}
// Array of strings
new ArrayOfAnything<string>(['a', 'b', 'c']);
// Array of Numbers
new ArrayOfAnything<number>([1, 2, 3]);

// Example of generics with functions
function printStrings(arr: string[]): void {
  for (let i = 0; i < arr.length; i++) {
    console.log(arr[i]);
  }
}

function printNumbers(arr: number[]): void {
  for (let i = 0; i < arr.length; i++) {
    console.log(arr[i]);
  }
}

function printAnything<T>(arr: T[]): void {
  for (let i = 0; i < arr.length; i++) {
    console.log(arr[i]);
  }
}

// Print an array of strings
printAnything<string>(['a', 'b', 'c']);

// Print an array of numbers
printAnything<number>([1, 2, 3]);

// Generic Constraints
class Car {
  print() {
    console.log('I am a car');
  }
}

class House {
  print() {
    console.log('I am a house');
  }
}

interface Printable {
  print(): void;
}

function printHousesOrCars<T extends Printable>(arr: T[]): void {
  for (let i = 0; i < arr.length; i++) {
    arr[i].print();
  }
}
// Print array of houses
printHousesOrCars<House>([new House(), new House()]);

// Print array of cars
printHousesOrCars<Car>([new Car(), new Car()]);