function Mammal(name){
this.name = name;
}
Mammal.prototype.displayName = function(){
return this.name;
}
function Organism(name){
this.orgName = name;
}
Organism.prototype.print = function(){
return this.orgName;
}
Organism.prototype = new Mammal(); //Organism inherits Mammal
//Testing
var o = new Organism('Human');
o.print()
This comes as undefined. Why? this should show since it is a method of class Organism. print() does not show up in the object
When you do:
Organism.prototype = new Mammal(); //Organism inherits Mammal
you replace the entire prototype object, thus wiping out the previously assigned:
Organism.prototype.print = function(){
return this.orgName;
}
You can fix it by changing the order so you "add" your new method to the inherited prototype:
function Organism(name){
this.orgName = name;
}
Organism.prototype = new Mammal(); //Organism inherits Mammal
Organism.prototype.print = function(){
return this.orgName;
}
FYI as an aside, you should be thinking about using Organism.prototype = Object.create(Mammal.prototype); instead and you should be calling the constructor of the base object too. See here on MDN for examples.
When you assign
Organism.prototype = new Mammal();
you are clobbering the Organism.prototype object that had the print function on it. Try this instead for your inheritance:
function Mammal(name){
this.name = name;
}
Mammal.prototype.displayName = function(){
return this.name;
}
function Organism(name){
this.orgName = name;
}
Organism.prototype = Object.create(Mammal.prototype);
Organism.constructor = Mammal;
// or _.extend(), if using underscore
jQuery.extend(Organism.prototype, {
print: function(){
return this.orgName;
}
});
//Testing
var o = new Organism('Human');
o.print()
Organism.prototype.print = function(){} is fine too.
Uncaught TypeError: undefined is not a function. Also have a look at this question to learn how to set up inheritance properly.