js prototoype2.js

// JavaScript has prototypical inheritance
// so there is no real difference in extending
// something or creating a new instance
// (although the new keyword may have tricked you
// into thinking so)

var debug = true;


// A minimal polyfill for Object.assign
// (an ES6 feature)
Object.assign = Object.assign || function(){
  for(var i = 1; i < arguments.length; i++){
    for(var j in arguments[i]){
      arguments[0][j] = arguments[i][j];
    }
  }
};


// If debug or no native Object.create
// then replace native Object.create with a variant 
// that gives us nicer writeouts of "classnames" in the console
var reusableFuncs = {};
Object.create = !debug && Object.create ? Object.create : function (o,name) {
  name = name || "Object";
  var F;
  if(reusableFuncs[name]){
    // avoid eval on "classes" already created - speedier
    F = reusableFuncs[name];
  }
  else {
    // Eval necessary for nice debugging "classnames"
    eval('F = function ' + name + '() {}');
  }
  F.prototype = o;
  reusableFuncs[name] = F;
  return new F();
};


// A small Base object with a simple extend method
// (if debug is on and you send a property $ it will
// be used as a "classname")
var Base = {
  extend: function(props){
    // A new object with this object as its prototype
    var obj = Object.create(this,debug && (props.$ || this.$));
    // Assign properties to the new object
    Object.assign(obj,props);
    // $super
    for(var i in props){
      if(typeof this[i] + typeof obj[i] == "functionfunction"){
        obj[i].$super = this[i];
      }

    }
    return obj;
  }
};


// Some objects / "classes"

var Animal = Base.extend({
  $: 'Animal',
  alive: true,
  breath: function(){
    return "I take a breath";
  }
});

var Mammal = Animal.extend({
  $: 'Mammal',
  run: function(){
    return "I run";
  }
});

var Human = Mammal.extend({
  $: 'Human',
  name: "John Doe",
  write: function(){
    return this.name + " says: I'm trying to write something!";
  },
  run: function(){
    return this.run.$super() + " on two legs.";
  }
});

var Kalle = Human.extend({
  name: "Kalle"
});

var Eva = Human.extend({
  name: "Eva"
});


// Let's check things out

console.log(Kalle);
console.log(Eva);
console.log(Kalle.write());
console.log(Eva.write());
console.log(Kalle.run());