将函数参数限制为某些枚举值

// 定义一个枚举类型
const Fruit = {
  APPLE: 'apple',
  BANANA: 'banana',
  ORANGE: 'orange'
};

// 使用枚举类型限制函数参数
function eatFruit(fruit) {
  if (fruit === Fruit.APPLE) {
    console.log('Eat an apple');
  } else if (fruit === Fruit.BANANA) {
    console.log('Eat a banana');
  } else if (fruit === Fruit.ORANGE) {
    console.log('Eat an orange');
  } else {
    console.log('Unknown fruit');
  }
}

// 调用函数
eatFruit(Fruit.APPLE); // 输出：Eat an apple
eatFruit(Fruit.BANANA); // 输出：Eat a banana
eatFruit(Fruit.ORANGE); // 输出：Eat an orange
eatFruit('grape'); // 输出：Unknown fruit

// 定义一个枚举类型
enum Fruit {
  APPLE,
  BANANA,
  ORANGE
}

// 使用枚举类型限制函数参数
public void eatFruit(Fruit fruit) {
  switch (fruit) {
    case APPLE:
      System.out.println("Eat an apple");
      break;
    case BANANA:
      System.out.println("Eat a banana");
      break;
    case ORANGE:
      System.out.println("Eat an orange");
      break;
    default:
      System.out.println("Unknown fruit");
      break;
  }
}

// 调用函数
eatFruit(Fruit.APPLE); // 输出：Eat an apple
eatFruit(Fruit.BANANA); // 输出：Eat a banana
eatFruit(Fruit.ORANGE); // 输出：Eat an orange
eatFruit(Fruit.GRAPE); // 输出：Unknown fruit