index.ts

class Context {
  private strategy: Strategy;

  constructor(strategy: Strategy) {
    this.strategy = strategy;
  }

  public setStrategy(strategy: Strategy) {
    this.strategy = strategy;
  }

  public doSomeBusinessLogic(): void {
    console.log('Context: Sorting data using the strategy (not sure how it\'ll do it)');
    const result = this.strategy.doAlgorithm(['a', 'b', 'c', 'd', 'e']);
    console.log(result.join(','));
  }
}

interface Strategy {
  doAlgorithm(data: string[]): string[];
}

class ConcreteStrategyA implements Strategy {
  public doAlgorithm(data: string[]): string[] {
    return data.sort();
  }
}

class ConcreteStrategyB implements Strategy {
  public doAlgorithm(data: string[]): string[] {
    return data.reverse();
  }
}


function clientCodeContext() {
  const context = new Context(new ConcreteStrategyA());
  console.log('Client: Strategy is set to normal sorting.');
  context.doSomeBusinessLogic();

  console.log('');

  console.log('Client: Strategy is set to reverse sorting.');
  context.setStrategy(new ConcreteStrategyB());
  context.doSomeBusinessLogic();
}

export function strategy() {
  clientCodeContext()
}