const Bonus = function() {
Bonus.prototype.setSalary = function(salary) {
this.salary = salary // 设置员工的原始工资
Bonus.prototype.setStrategy = function(strategy) {
this.strategy = strategy // 设置员工绩效等级对应的策略对象
Bonus.prototype.getBonus = function() {
return this.strategy.calculate(this.salary)// 把计算奖金的操作委托给对应的策略对象