SOURCE

var performanceS = function(){};

		performanceS.prototype.calculte = function(salary){
			return salary*4
		}

		var performanceA = function(){};

		performanceA.prototype.calculte = function(salary){
			return salary*3
		}

		var performanceB = function(){};

		performanceB.prototype.calculte = function(salary){
			return salary*2
		}

		var Bonus = function(){
			this.salary = null;
			this.strategy = null;
		}

		Bonus.prototype.setSalary = function(salary){
			this.salary = salary;
		}

		Bonus.prototype.setStrategy = function(strategy){
			this.strategy = strategy;
		}

		Bonus.prototype.getBonus = function(){
			return this.strategy.calculte(this.salary)
		}

		var bonus =  new Bonus();
		bonus.setSalary(1000);
		bonus.setStrategy(new performanceS())

		console.log(bonus.getBonus())

		bonus.setStrategy(new performanceA())

		console.log(bonus.getBonus())