Generics in TypeScript

generics.ts

function getRandom<T>(array: T[]): T {
  const diceRoll = Math.floor(Math.random() * array.length);
  return array[diceRoll];
}

const names = [
  'Amelia', 'Ava', 'Benjamin', 'Charlotte', 'Elijah', 'Emma',
  'Evelyn', 'Harper', 'Henry', 'Isabella', 'James', 'Liam', 'Lucas', 'Mia',
  'Noah', 'Oliver', 'Olivia', 'Sophia', 'Theodore', 'William'
];

const randomName = getRandom(names);

console.log(randomName);

const numbers = [159, 321, 330, 37, 471, 500, 614, 672, 727, 861];

const randomNumber = getRandom(numbers);

console.log(randomNumber);

function rollDice(array: any[]): number {
  return Math.floor(Math.random() * array.length);
}

function getRandoms<A, B>(array: A[], secondArray: B[]): [A, B] {
  const a = array[rollDice(array)];
  const b = secondArray[rollDice(secondArray)];
  return [a, b];
}

const [someName, someNumber] = getRandoms<string, number>(names, numbers);
console.log(someName, someNumber);

interface HttpResponse<T> {
  code: number;
  data: T;
}

interface ResponseData {
  completed: boolean;
  id: number;
  title: string;
  userId: number;
}

async function getJson<T>(url: string): Promise<HttpResponse<T>> {
  const response = await fetch(url);
  const data: T = await response.json();
  return {
    code: response.status,
    data,
  };
}

(async () => {
  const response = await getJson<ResponseData>('https://jsonplaceholder.typicode.com/todos/1');
  console.log(response.code, response.data.title);
})();

interface User {
  name: string;
}

interface Person extends User {
  shout: () => void;
}

interface Dog extends User {
  bark: () => void;
}

function printName<T extends User>(someone: T): T {
  console.log(someone.name);
  return someone;
}