构造函数执行前的属性初始化

function Person(name, age) {
    this.name = name;
    this.age = age;
}

Person.prototype.greet = function() {
    console.log(`Hello, my name is ${this.name} and I am ${this.age} years old.`);
};

const person1 = new Person('Alice', 30);
person1.greet(); // 输出: Hello, my name is Alice and I am 30 years old.

class Person {
    constructor(name, age) {
        this.name = name;
        this.age = age;
    }

    greet() {
        console.log(`Hello, my name is ${this.name} and I am ${this.age} years old.`);
    }
}

const person2 = new Person('Bob', 25);
person2.greet(); // 输出: Hello, my name is Bob and I am 25 years old.

class Person {
    name = '';
    age = 0;

    constructor(name, age) {
        this.name = name;
        this.age = age;
    }

    greet() {
        console.log(`Hello, my name is ${this.name} and I am ${this.age} years old.`);
    }
}

const person3 = new Person('Charlie', 35);
person3.greet(); // 输出: Hello, my name is Charlie and I am 35 years old.

function Person(name, age) {
    if (typeof name !== 'string' || typeof age !== 'number') {
        throw new Error('Invalid arguments');
    }
    this.name = name;
    this.age = age;
}

function Person(name, age) {
    this.name = name;
    this.age = age;
}

// 立即设置原型方法
Person.prototype.greet = function() {
    console.log(`Hello, my name is ${this.name} and I am ${this.age} years old.`);
};