cool items in typescript

as-const-url.ts

type UserUrl = string;

// const getUserUrl = (id: number) => {
//   return `/user/${id}`; // as const
// };

// type UserUrl = ReturnType<typeof getUserUrl>;

const url: UserUrl = '/user/2';

as-const.ts

const CONFIG = {
  pumpType: 'conventional',
  pumpName: 'Sample pump',
};

// as const

class Example {
  public config = CONFIG;

  constructor() {
    this.config.pumpName = 'something else';
  }

  getConfiguration(): typeof CONFIG {
    return this.config;
  }
}

keyof.ts

interface IField {
  name: string;
  age: number;
}

type FormValue = Record<
  'name' | 'age',
  {
    label: string;
    message: string;
  }
>;

const formValues: FormValue = {
  name: {
    label: 'Your name',
    message: 'Your full name',
  },
  age: {
    label: 'Your age',
    message: 'you have to be above 18+',
  },
};

// keyof IFields

prettify.ts

interface IUser {
  name: string;
  age: string;
}

interface IAdminUser extends IUser {
  isAdmin: boolean;
}

interface ISuperUser extends IAdminUser {
  isSuperUser: boolean;
}

const user: ISuperUser = null;

// type Prettify<T> = {
//   [K in keyof T]: T[K];
// } & {};

will-it-error.ts

interface Product {
  name: string;
}

interface Product {
  price: number;
}

const product: Product = {
  name: 'Apple',
  price: 5
}