/**
 * 操作符in 來進行型別縮小
 * js中in運算子用來確定物件是否具有某個名稱的屬性
 * 所以ts中也有這個，用來縮小潛在的類型範圍
 */

//例如“value” in x ,value是字串文字 x代表聯合型別
//true x具有可選或者必需屬性的型別的值
//false 分支的縮小 x需要具有可選或者缺失屬性型別的值
type WJH = { name: string; age: number };
type WH = { name: string; color: string };
function Earth(people: WJH | WH) {
  if ("age" in people) {
    console.log(people.name);
  }
  if ("color" in people) {
    console.log(people.name);
  }
}
Earth({
  age: 18,
  name: "王佳慧",
});
Earth({
  color: "blue",
  name: "呵呵呵呵呵",
});

/**
 * instanceof 操作符縮小
 * 測試它左邊的物件是否是它右邊的類的例項，返回 boolean 的資料型別。
 * x instanceof A
 */
function logValue(x: Date | string) {
  if (x instanceof Date) {
    console.log(x.toUTCString());
  } else {
    console.log(x.toUpperCase());
  }
}
logValue(new Date());
logValue("wangjiahui");

/**
 * 型別謂詞
 * 想要直接控制整個程式碼的型別變化
 * 想要定義一種型別的型別保護
 * 我們只需要定一個函式讓他的返回值是型別謂詞就可以
 */
type Fish = { swim: () => void; name: string };
type Bird = { fly: () => void; name: string };
function isFish(anmial: Fish | Bird): anmial is Fish {
  console.log((anmial as Fish).swim !== undefined);
  return (anmial as Fish).swim !== undefined;
}
//
function checkType<T>(val: any, type: keyof T): val is T {
  return (val as T)[type] !== undefined;
}
function getAnmialType(): Fish | Bird {
  let fish: Fish = {
    name: "鯊魚",
    swim: () => {
      console.log("我是鯊魚呵呵呵");
    },
  };
  let bird: Bird = {
    name: "麻雀",
    fly: () => {
      console.log("我是麻雀嘻嘻嘻");
    },
  };
  return true ? fish : bird;
}
let pet = getAnmialType();

if (isFish(pet)) {
  pet.swim();
} else {
  pet.fly();
}

//型別相容  要滿足之前的基礎屬性  TS的反推
//物件的賦值
interface A {
  name: string;
  age: number;
}
let B: A;
let C = {
  name: "wangjiahui",
  age: 10,
  color: "blue",
};
B = C;