Is this Object Oriented Javascript

Question

Is the following code equivalent to a class with associated functions? What is the difference between 'obj.start' function and startEngine() function? (Not logic wise, structural wise.. )

var Car = function (carElement)
{
            var obj = {},
                isRunning = false,
                dashboard,
                speed = 0,
                accelerometer,
                gearElement,
                transmission =
                {
                    'first': { ts: 15, rpm: 2 },
                    'second': { ts: 30, rpm: 4 },
                    'third': { ts: 50, rpm: 5 },
                    'fourth': { ts: 80, rpm: 5 },
                    'fifth': { ts: 110, rpm: 6 }
                };

        function startEngine()
        {
            //some code to start engine
        }

    obj.start = function ()
    { 
         //more code.. 
    }

    obj.stop = function ()
    {
        //even more code...
    };

   (function init()
   {
      obj.start();
   }());

return obj;
};

[EDIT] This question practically describes what my question is all about

see this answer about JS-Objects: stackoverflow.com/questions/23310353/… — Daniel Gasser
– Daniel Gasser, Commented May 20, 2014 at 15:05
@pc-shooter, thanks! However, does this really relate to how JS-Object can have properties and methods accessed with DOT notation? I see how obj.start is assigned a function and can be later accessed using obj.start(), however, it does not answer why one would use that instead of a function with a normal header function startEngine().. and is Car considered to be a class here? Thanks — LogixMaster
– LogixMaster, Commented May 20, 2014 at 15:13

MrCode · Accepted Answer · 2014-05-20 15:24:41Z

Is the following code equivalent to a class with associated functions?

It depends on how you instantiate it. If you use the function declaration style (like startEngine uses), and if you instantiate it with the new keyword, and remove the return value then yes (though startEngine is private-like not public until you create a public pointer to it).

What is the difference between 'obj.start' function and startEngine() function?

The differences are:

startEngine is a function declaration, and so it is hoisted, unlike obj.start which is a anonymous function expression that isn't hoisted.
startEngine is a private-like method of the Car "class". obj.start is not.
obj.start is a method on the obj object, which is a property of the Car "class".
obj is being returned if Car is called as a function (without the new keyword), therfore the methods of obj can be called from outside of Car, whereas startEngine isn't reachable from outside of Car, without a public pointer.

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