JavaScript basic ideas

gistfile1.js

//creating an object and adding methods to it
var rabbit = {};

rabbit.speak = function(line) {
    console.log("The rabbit says '" + line + "'");
}

rabbit.speak("I'm alive");

//can also add previously defined functions to the objects
function speak(line) {
    console.log("The " + this.type + " rabbit says '" + line + "'");
}

speak("Hi, I seem to be undefined");

var whiteRabbit = { type: "white", speak: speak };
var fatRabbit = { type : "fat", speak: speak};

whiteRabbit.speak("Oh my ears and whiskers, how late it's getting!");
fatRabbit.speak("I could use a carrot right now.");

//can call functions using apply and call on random objects
speak.apply(fatRabbit, ["Burp"]);
speak.call({type : "old"}, "Oh my.");

//prototype magic

var empty = {};
console.log(empty.toString);
console.log(empty.toString());

console.log(Object.getPrototypeOf({}) == Object.prototype);
console.log("Prototype of Object.prototype: " + Object.getPrototypeOf(Object.prototype));

//using the prototype for creating objects

var protoRabbit = {
    speak: function(line) {
        console.log("The " + this.type + " rabbit says '" + line + "'");
    }
};
var killerRabbit = Object.create(protoRabbit);
killerRabbit.type = "killer";
killerRabbit.speak("SKREEE!");

//constructors - any functions called with new is treated as a constructor
function Rabbit(type) {
    this.type = type;
}

var killerRabbit = new Rabbit("killer");
var blackRabbit = new Rabbit("black");
console.log(blackRabbit.type);

//constructors get an empty prototype that is derived from Object.constructor
//this prototype is held on the "prototype" property and is not the actual
//prototype of the Rabbit function ( which is actually Function.prototype)
Rabbit.prototype.speak = function(line) {
    console.log("The " + this.type + " rabbit says '" + line + "'");
}

blackRabbit.speak("Doom...");
Rabbit.prototype.teeth = "small";
killerRabbit.teeth = "long, sharp, and bloody";
console.log(killerRabbit.teeth);

//prototype inheritance
Rabbit.prototype.dance = function() {
    console.log("The " + this.type + " rabbit dances a jig.");
}

killerRabbit.dance();

//how prototypes can cause problems
var map = {};
function storePhi(event, phi) {
  map[event] = phi;
}

storePhi("pizza", 0.069);
storePhi("touched tree", -0.081);

// add a property to the Object prototype
Object.prototype.nonsense = "hi there"

for (var name in map) {
    console.log(name);
}

Object.defineProperty(Object.prototype, "hiddenNonsense", 
                        {enumerable : false, value: "hi"});
                        
for (var name in map) {
    console.log(name);
}

console.log("toString" in map);
console.log(map.hasOwnProperty("toString"));

//prototype-less objects - usefull as someone could actually update
//the hasOwnProperty function in the prototype - such a drag
var map = Object.create(null);
map["pizza"] = 0.069;
console.log("toString" in map);
console.log("pizza" in map);