client.ts

// The Strategy Pattern Example Use Case

class GameCharacter {
  // This is the context whose strategy will change

  #position: [number, number] = [0, 0];

  move(movementStyle: IMoveConstructor) {
    // The movement algorithm has been decided by the client
    new movementStyle().move(this.#position);
  }
}

interface IMoveConstructor {
  // A Constructor for the IMove
  new (): IMove;
}

interface IMove {
  // The Move Strategy Interface
  move(position: [number, number]): void;
}

class Walking implements IMove {
  // A concrete movement strategy for walking

  move(position: [number, number]) {
    position[0] += 1;
    console.log(`I am Walking. New position = ${position}`);
  }
}

class Sprinting implements IMove {
  // A concrete movement strategy for sprinting

  move(position: [number, number]) {
    position[0] += 2;
    console.log(`I am Running. New position = ${position}`);
  }
}

class Crawling implements IMove {
  // A concrete movement strategy for crawling

  move(position: [number, number]) {
    position[0] += 0.5;
    console.log(`I am Crawling. New position = ${position} `);
  }
}

// The Client
const GAME_CHARACTER = new GameCharacter();

// If comment out the IMoveConstructor, well have to write it like this
// GAME_CHARACTER.move(new Walking());

GAME_CHARACTER.move(Walking);
// Character sees the enemy
GAME_CHARACTER.move(Sprinting);
// Character finds a small cave to hide in
GAME_CHARACTER.move(Crawling);

/* OUTPUT
~ node ./dist/behavioural/strategy/client.js

I am Walking. New position = 1,0
I am Running. New position = 3,0
I am Crawling. New position = 3.5,0

*/