详解TypeScript中类的定义与用法

function Person(name, age) {
  this.name = name;
  this.age = age;
}
Person.prototype.greet = function() {
  console.log(`Hello, my name is ${this.name} and I'm ${this.age} years old.`);
};
const john = new Person('John', 25);
john.greet(); // 输出：Hello, my name is John and I'm 25 years old.

class Person {
  constructor(public name: string, public age: number) {}
  greet() {
    console.log(`Hello, my name is ${this.name} and I'm ${this.age} years old.`);
  }
}
const john = new Person('John', 25);
john.greet(); // 输出：Hello, my name is John and I'm 25 years old.

function Animal(name) {
  this.name = name;
}
Animal.prototype.greet = function() {
  console.log(`Hello, I'm ${this.name}`);
};
function Dog(name, breed) {
  Animal.call(this, name);
  this.breed = breed;
}
Dog.prototype = Object.create(Animal.prototype);
Dog.prototype.constructor = Dog;
Dog.prototype.bark = function() {
  console.log('Woof! Woof!');
};
const myDog = new Dog('Buddy', 'Golden Retriever');
myDog.greet(); // 输出：Hello, I'm Buddy
myDog.bark(); // 输出：Woof! Woof!

class Animal {
  constructor(public name: string) {}
  greet() {
    console.log(`Hello, I'm ${this.name}`);
  }
}
class Dog extends Animal {
  constructor(name: string, public breed: string) {
    super(name);
  }
  bark() {
    console.log('Woof! Woof!');
  }
}
const myDog = new Dog('Buddy', 'Golden Retriever');
myDog.greet(); // 输出：Hello, I'm Buddy
myDog.bark(); // 输出：Woof! Woof!

class Car {
  public brand: string;
  private price: number;
  protected color: string;
  constructor(brand: string, price: number, color: string) {
    this.brand = brand;
    this.price = price;
    this.color = color;
  }
  public start() {
    console.log(`Starting the ${this.color} ${this.brand} car.`);
  }
  private calculateTax() {
    // 在类的内部可以访问私有方法和属性
    // 计算税费的逻辑
  }
  protected drive() {
    console.log(`Driving the ${this.color} ${this.brand} car.`);
  }
}
const myCar = new Car('Tesla', 50000, 'Red');
myCar.start(); // 输出：Starting the Red Tesla car.
myCar.drive(); // 编译错误：Property 'drive' is protected and only accessible within class 'Car' and its subclasses.
console.log(myCar.brand); // 输出：Tesla
console.log(myCar.price); // 编译错误：Property 'price' is private and only accessible within class 'Car'.
console.log(myCar.color); // 编译错误：Property 'color' is protected and only accessible within class 'Car' and its subclasses.

class MathUtils {
  static PI = 3.14159;
  static calculateArea(radius: number) {
    return MathUtils.PI * radius * radius;
  }
}
console.log(MathUtils.PI); // 输出：3.14159
console.log(MathUtils.calculateArea(5)); // 输出：78.53975