Subclassing JavaScript

subclass_extend.js

function extend(child, parent) {
  var F = function () {
    this.__construct = function () {
      parent.apply(this, arguments);
    };
    this.constructor = child;
  };
  F.prototype = parent.prototype;

  // append from subclass prototype
  var key;
  for (key in child.prototype) {
    F.prototype[key] = child.prototype[key];
  }

  // append static props from subclass
  for (key in child)  {
    F[key] = child[key];
  }

  child.prototype = new F();
  child.__super__ = parent.prototype;
}


// Entity class
function Entity(type) {
  this.type = type || "entity";
}

Entity.prototype.getType = function () {
  return this.type;
};

// Person class
function Person(name) {
  this.__construct("person");
  this.name = name;
}

Person.prototype.name = function () {
  return this.name;
}

extend(Person, Entity); // extend from Entity

// Example
var p = new Person("Guy Person");
p.getType() => "person"
p.getName() => "Guy Person"