javascript prototypical inheritance confusion

Question

Below is a working example to show how the prototype of Javascript work. So from my understand is simply the customer instance inherited the prototype function of the Person.

 var Person = function (name) { this.name = name; }; Person.prototype.getName = function () { return this.name; }; var john = new Person("John"); alert(john.getName()); Person.prototype.sayMyName = function () { alert('Hello, my name is ' + this.getName()); }; john.sayMyName(); var Customer = function (name) { this.name = name; }; Customer.prototype = new Person(); var myCustomer = new Customer('Dream Inc.'); myCustomer.sayMyName(); Customer.prototype.setAmountDue = function (amountDue) { this.amountDue = amountDue; }; Customer.prototype.getAmountDue = function () { return this.amountDue; }; myCustomer.setAmountDue(2000); alert(myCustomer.getAmountDue()); 

But one thing bug me is that why the author do a getAmountdue prototype function? it simply return this.amountDue.

Answer 1

I think the issue is not related to javascript prototypical inheritance.

To wrap the property into a function return could abstract the implementation.

For example, if your boss want you provide a decorated result of this.amountDue , you can just change the implementation of getAmountDue method.