Typeguards

// type guard with typeof
 
type ADD = string | number;
const Add = (param1: ADD, param2: ADD): ADD => {
  if (typeof param1 === "number" && typeof param2 === "number") {
    return param1 + param2;
  } else {
    return param1.toString() + param2.toString();
  }
};
 
const res1 = Add(2, 3);
const res2 = Add("5", "5");
 
console.log(res1, res2);
 

// in guard
 
type NormalUser = {
  name: string;
};
type AdminUser = {
  name: string;
  role: "admin";
};
 
const getUser = (user: NormalUser | AdminUser) => {
  if ("role" in user) {
    // এখন আমরা admin টাইপের প্রপার্টি অ্যাক্সেস করতে পারি
    console.log(`I am ${user.name} & My role is ${user.role}`);
  } else {
    console.log(`I am ${user.name}`);
  }
};
 
const normalUser: NormalUser = {
  name: "I am a NormalUser",
};
const adminUser: AdminUser = {
  name: "I am an Admin",
  role: "admin",
};
 
getUser(normalUser);
getUser(adminUser);
 

class Animal {
  makeSound() {
    console.log("Animal sound");
  }
}
class Dog extends Animal {
  makeBark() {
    console.log("Bark!");
  }
}
class Cat extends Animal {
  makeMeaw() {
    console.log("Meaw!");
  }
}
 
const isDog = (animal: Animal): animal is Dog => {
  return animal instanceof Dog;
};
const isCat = (animal: Animal): animal is Cat => {
  return animal instanceof Cat;
};
 
const getAnimal = (animal: Animal) => {
  if (isDog(animal)) {
    animal.makeBark();
  } else if (isCat(animal)) {
    animal.makeMeaw();
  } else {
    animal.makeSound();
  }
};