Typescript缩小给定接口中的类型范围

interface Animal {
  name: string;
  age: number;
}

interface Cat extends Animal {
  breed: string;
}

function printCatInfo(animal: Animal) {
  if ((animal as Cat).breed) {
    const cat = animal as Cat;
    console.log(`Cat: ${cat.name}, Breed: ${cat.breed}`);
  } else {
    console.log(`Not a cat: ${animal.name}`);
  }
}

const myCat: Cat = { name: "Tom", age: 3, breed: "Persian" };
printCatInfo(myCat);

interface Animal {
  name: string;
  age: number;
}

interface Cat extends Animal {
  breed: string;
}

function printCatInfo(animal: Animal) {
  if (isCat(animal)) {
    console.log(`Cat: ${animal.name}, Breed: ${animal.breed}`);
  } else {
    console.log(`Not a cat: ${animal.name}`);
  }
}

function isCat(animal: Animal): animal is Cat {
  return (animal as Cat).breed !== undefined;
}

const myCat: Cat = { name: "Tom", age: 3, breed: "Persian" };
printCatInfo(myCat);