const strategies = {
    'S': function (salary) {
      return salary * 4;
    },
    'A': function (salary) {
      return salary * 3;
    },
    'B': function (salary) {
      return salary * 2;
    }
  }

  var calculateBonus = function (level, salary) {
    return strategies[level](salary);
  }

  calculateBonus('A', 10000);