Javascript Inheritance

Javascript inheritance is another one of those topics that always escapes my mind, so I’m recording it here for future reference.

I tried to get into Crockford’s Prototypal Inheritance method but I like the plain-old prototype inheritance without the object.create better. It’s entirely possible that I’m not quite getting Crockford’s method and its advantages; feel free to enlighten me by leaving a comment.

Anyway, here’s what I’m going with: We’ll have a base class (actually an object) English that says “hello” and “goodbye”. We’ll have a Spanglish class (actually an object) that inherits from English and says “ola” instead of “hello” (over-rides the hello method), but keeps saying “bye” (inherits the bye method from English).

The Spanglish.prototype = new English\(\); line does the actual inheritance by setting Spanglish’s prototype to be an instance of English.

function English() {
	this.hello = function(){ return "hello"; }
	this.bye   = function(){ return "bye"; }
}

function Spanglish() {
	this.hello = function() { return "ola"; }
}
Spanglish.prototype = new English();

e = new English();
s = new Spanglish();

e.hello();   // prints "hello"
e.bye();     // prints "bye"
s.hello();   // prints "ola"
s.bye();     // prints "bye", inherited from English