Javascript代码混淆的原型

Question

 function Person(firstName, lastName) { this.firstName = firstName; this.lastName = lastName; } // Greeting Person.prototype.greeting = function() { return `Hello there ${this.firstName} ${this.lastName}`; } // Customer constructor function Customer(firstName, lastName, phone, membership) { Person.call(this, firstName, lastName); this.phone = phone; this.membership = membership; } // Inherit the Person prototype methods Customer.prototype = Person; let detail1 = new Customer("hom", "kom", 989, "l"); detail1.greeting() // it is producing error that greeting is not a function 

Why when I am running detail1.greeting() is producing an error even though I have set the prototype.

Answer 1

Customer.prototype = Person; won't tie a Customer 's methods to Person.prototype 's methods, because the methods aren't on Person itself, but on Person.prototype . While you could do Customer.prototype = Person.prototype , that's probably not desirable, because then mutations to Customer.prototype would affect Person.prototype as well.

For Customer.prototype to inherit Person.prototype 's methods, you should have Customer.prototype be an object whose internal prototype is Person.prototype , which can be done with Object.create :

Customer.prototype = Object.create(Person.prototype);

 function Person(firstName, lastName) { this.firstName = firstName; this.lastName = lastName; } // Greeting Person.prototype.greeting = function() { return `Hello there ${this.firstName} ${this.lastName}`; } // Customer constructor function Customer(firstName, lastName, phone, membership) { Person.call(this, firstName, lastName); this.phone = phone; this.membership = membership; } // Inherit the Person prototype methods Customer.prototype = Object.create(Person.prototype); let detail1 = new Customer("hom", "kom", 989, "l"); console.log(detail1.greeting()) // it is producing error that greeting is not a function