I've seen some short notions about pattern matching on code plex, but no serious discussions around it. As I'm a big fan of it, I've written up some small examples on how I think pattern matching could look in TypeScript.

This is by far no complete specification, just some ideas that I want to bring forward and have a little discussion around.

Function Overloading

// Pattern matching on functions
function pickCard {
  (x: {suit: string; card: number; }[]): number {
    var pickedCard = Math.floor(Math.random() * x.length);
    return pickedCard;
  }
  (x: number): {suit: string; card: number; } {
    var pickedSuit = Math.floor(x / 13);
    return { suit: suits[pickedSuit], card: x % 13 };
  }
}

// Translation of functions.ts using sparkler
// https://github.com/natefaubion/sparkler
function pickCard(x) {
  [...{ suit @ String, card @ number }] =>  {
    var pickedCard = Math.floor(Math.random() * x.length);
    return pickedCard;
  }
  x @ Number => {
    var pickedSuit = Math.floor(x / 13);
    return { suit: suits[pickedSuit], card: x % 13 };
  }
}

`Match` statement

// Pattern matching using match
function whoami (x: any): string {
  match x {
    case { name: string, type: 'person' }:
        return 'Person: ' + name;
    case { name: string, type: 'animal' }:
        return 'Animal: ' + name;
    default:
        return 'Unkown you';
  }
}

// Pattern matching using match translated
function whoami (x) {
  match x {
    case { name @ String, type: 'person' }:
        return 'Person: ' + name;
    case { name @ String, type: 'animal' }:
        return 'Animal: ' + name;
    default:
        return 'Unkown you';
  }
}

Function Overloading

Match statement

`Match` statement