javascript - 原型(prototype)继承是错误的

Question

我创建了一个 person 构造函数，并采用了 firstname = fn、lastname = ln 和 dateofbirth = dob。

该代码是:

function Person(fn, ln, dob){
    this.fn = fn;
    this.ln = ln;
    this.dob = new Date(dob);
}

我还添加了原型(prototype)

Person.prototype.calcAge = function(){
    const diff = Date.now() - this.dob.getTime();
    const age = new Date(diff);
    return Math.abs(age.getUTCFullYear() - 1970);
}

这是我的第一个 Person 构造函数。

第二个构造函数我被视为客户构造函数，代码是:

function Customer(fn,ln,phone,membership){
    Person.call(this,fn,ln);
    this.phone = phone;
    this.membership = membership;

}

我正在从人到客户继承原型(prototype)

//Inheriting Person Prototype
Customer.prototype = Object.create(Person.prototype);

// Making Customer Prototype
Customer.prototype.constructor = Customer;

我正在控制台日志记录:

const Customer1 = new Customer('Sairam', 'Gudiputis', '790-139-7848', 'Premium');
console.log(Customer1)

但是在控制台中我得到了无效的出生日期，我没有在客户中使用..

    function Person(fn, ln, dob){
    	this.fn = fn;
    	this.ln = ln;
    	this.dob = new Date(dob);
    }
	
	 Person.prototype.calcAge = function(){
    	const diff = Date.now() - this.dob.getTime();
    	const age = new Date(diff);
    	return Math.abs(age.getUTCFullYear() - 1970);
    }
	
	function Customer(fn,ln,phone,membership){
    	Person.call(this,fn,ln);
    	this.phone = phone;
    	this.membership = membership;
    
    }
	
	//Inheriting Person Prototype
    Customer.prototype = Object.create(Person.prototype);
    
    // Making Customer Prototype
    Customer.prototype.constructor = Customer;
	
	const Customer1 = new Customer('Sairam', 'Gudiputis', '790-139-7848', 'Premium');
    console.log(Customer1)

Answer 1

如果您不希望 Customer 中包含 dob，请添加:

      if (!(this instanceof Customer)) {
          this.dob = new Date(dob);
      }

在 Person 构造函数中:

function Person(fn, ln, dob){
    	this.fn = fn;
    	this.ln = ln;
      if (!(this instanceof Customer)) {
    	  this.dob = new Date(dob);
      }
    }
	
	 Person.prototype.calcAge = function(){
    	const diff = Date.now() - this.dob.getTime();
    	const age = new Date(diff);
    	return Math.abs(age.getUTCFullYear() - 1970);
    }
	
	function Customer(fn,ln,phone,membership){
    	Person.call(this,fn,ln);
    	this.phone = phone;
    	this.membership = membership;
    
    }
	
	//Inheriting Person Prototype
    Customer.prototype = Object.create(Person.prototype);
    
    // Making Customer Prototype
    Customer.prototype.constructor = Customer;
	
	const Customer1 = new Customer('Sairam', 'Gudiputis', '790-139-7848', 'Premium');
    console.log(Customer1)