// 接口
interface SDQ {
  anjiao: boolean;
  say: () => {};
}
// 接口
interface SDZ {
  anjiao: boolean;
  skill: () => {};
}

// 联合类型的关键符合是 | 
function subject(Number: SDQ | SDZ) {
  if(Number.anjiao){
    (Number as SDZ).skill
  }else{
    (Number as SDQ).say
  }
}

// 接口
interface SDQ {
  anjiao: boolean;
  say: () => {};
}
// 接口
interface SDZ {
  anjiao: boolean;
  skill: () => {};
}

function subject(Number: SDQ | SDZ) {
// 可以通过断言number as Teacher然后直接调用skill方法
  if(Number.anjiao){
    (Number as SDZ).skill
  }else{
    (Number as SDQ).say
  }
}

function subjectTwo(Number: SDQ | SDZ) {
// in来判断number里有没有skill()方
  if ("skill" in Number) {
    Number.skill();
  } else {
    Number.say();
  }
}

function sdq(first: string | number, second: string | number) {
// typeof来判断是不是string
  if (typeof first === "string" || typeof second === "string") {
    return `${first}${second}`;
  }
  return first + second;
}

function sdz(first: object | NumberObj, second: object | NumberObj) {
  if (first instanceof NumberObj && second instanceof NumberObj) {
    return first.count + second.count;
  }
  return 0;
}