Inheritance hierarchy design approach - Javascript [closed]

Question

For the below code, that creates inheritance hierarchy,

function Animal(){
    this.name = "Animal";

    // toString is a function in the main Object that every
    // object inherits from
    this.toString = function() {
        return "My name is : " + this.name;
    };
}


function Rodent(){
   this.name = "Rodent";
}

function Rat(){
  this.name = "Rat";
}

Rodent.prototype = new Animal();
Rat.prototype = new Rodent();

Rodent.prototype.constructor = Rodent;
Rat.prototype.constructor = Rat;

var caneRat = new Rat();

document.write(caneRat.toString() + "<br />");

a little modification is done by completely replacing Rat.prototype with Rodent.prototype, as a second approach, shown below,

function Animal(){
    this.name = "Animal";

    // toString is a function in the main Object that every
    // object inherits from
    this.toString = function() {
        return "My name is : " + this.name;
    };
}


function Rodent(){
   this.name = "Rodent";
}

function Rat(){
  this.name = "Rat";
}

Rodent.prototype = new Animal();
Rat.prototype = Rodent.prototype;
Rodent.prototype.constructor = Rodent;

var caneRat = new Rat();

document.write(caneRat.toString() + "<br />");  

What are the advantages & disadvantages in the second approach of inheritance hierarchy design compared to first approach? Second approach is visualized as shown below..

Answer 1

It's generally fairly awkward and error-prone to implement "classical inheritance" in JavaScript. Instead, try working with the language and use behavior delegation:

var Animal = {
  setName: function(name) {
    this.name = name;
  },

  sayName: function() {
    return 'My name is: ' + this.name;
  }
};

var Rodent = Object.create(Animal);
var Rat = Object.create(Rodent);
var caneRat = Object.create(Rat);

caneRat.setName('Rat');

console.log(caneRat.sayName()); // 'My name is Rat'

You'll probably find that you can eliminate a lot of your "subclasses" with this approach.

For more detail on prototypes in JavaScript, take a look at this.

Also, try to avoid overwriting native object methods (e.g. toString) unless you have a really good reason to do so.