INHERIT classes in javascript

There are hundreds of ways to do inheritance in javascript but a single one is simpler, cleanier and prettier than all the other ones.

A one-liner

To inherit a class in javascript, it’s a one-liner

TheSubClass.prototype = new TheParentClass();

As simple as that!

Where to write the one-liner

The problem with that one-liner is where should it goes? Once again, the answer is simple : after the constructor of the sub-class. It may look strange but it is extremely effective.

/* The constructor of the Mammal class */
function Mammal() {
}
/* The constructor of the Cat class */
function Cat() {
}
// The magic that inherits Cat from Mammal is here!!!!!
Cat.prototype = new Mammal();

Is this true inheritance?

In the hundreds of other ways of inheriting classes in javascript, I think that this is the only one that is a true inheritance. What do I mean by true inheritance? I mean that javascript recognizes it as a sub-class of the class. Check this out!

/* Above code goes here */
// Create a cat
var theCat = new Cat();
// Check if the cat is an instance of the Cat class
if (theCat instanceof Cat) {
alert("theCat is an instance of the Cat class");
}
// Check if the cat is an instance of the Mammal class
if (theCat instanceof Mammal) {
alert("theCat is an instance of the Mammal class");
}

If you execute this code, you’ll see that the cat is an instance of the Cat class and the Mammal class.