Javascript Constructor to Initialize Private Variables

Question

Ok, so I'm using the following skeleton code to create a Javascript Library

var Device = (function(window, document, $) {
    function func_1(){
         return 1;
    }

    function func_2(){
        return 2;
    }

    var internalDevice = {
        func_1: func_1,
        func_2: func_2
    };
    return internalDevice; // expose functionality to the rest of the code
})(window, document, jQuery);

Essentially, I would call my functions like so: Device.func_1();.

I'm looking to add a constructor that will initialize some private variables from the get-go i.e. as soon as the object is created, and without having to make any extra function call(s).

How do I do this?!

Thanks.

c 2 · Accepted Answer · 2012-11-19 01:31:41Z

2

May be try this way? private_1 and private_2 can only be accessible through function calls while you can use Device() constructor.

function Device(param1, param2) {
    var private_1= param1;
    var private_2= param2;

    this.func_1= function() {
        return private_1;                
    }

    this.func_2= function() {
        return private_2;            
    }
}

var myDevice = new Device(1, 2);
alert(myob.func_1());

or may be like this:

var Device = (function(window, document) {
    var private_1;

    function init(param1) {
      private_1 = param1;
    }

    function func_1(){
         return private_1;
    }

    function func_2(){
        return 2;
    }

    var internalDevice = {
        func_1: func_1,
        func_2: func_2,
        init  : init
    };
    return internalDevice; // expose functionality to the rest of the code
})(window, document);

Device.init(10);
alert(Device.func_1())

edited Nov 19, 2012 at 1:31

answered Nov 19, 2012 at 1:15

c 2

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5 Comments

ObiHill Over a year ago

Thanks, but I'd rather stick to my original 'motif', do you know how I can achieve this with my current format?

c 2 Over a year ago

Just added another approach.

ObiHill Over a year ago

Thanks. I figured out a way to do this without calling init. I'll post the answer shortly.

c 2 Over a year ago

You were asking for a way to initialize the private variables, your answer below is just hard-coding the value...

ObiHill Over a year ago

I was looking for a way to have a constructor initialize values for the private variables, without forcing the user to call a specific init method first.

ObiHill · Accepted Answer · 2012-11-19 12:38:43Z

I managed to figure this one out, here's how I did it:

var Device = (function(window, document, $) {
    var var_1 = 10,
    var_2 = 20,
    var_3;

    function init(){
         var_3 = 30;
    }

    function func_1(){
         return 1;
    }

    function func_2(){
         return 2;
    }

    var internalDevice = {
        init: init(),
        func_1: func_1,
        func_2: func_2
    };
    return internalDevice;
})(window, document, jQuery);

So when you call Device.func_2();, the variables would already have been initialized. You can see a live example here: http://jsfiddle.net/CZjYH/11/

I am also going to be implementing Amplify.JS functionality inside the init function as a way of persisting my variables to local or Session storage.

Cheers.

redline · Accepted Answer · 2012-11-19 01:42:29Z

var Device = (function(window, document, $, undefined)
{
    return $.extend(function()
    {
        // constructor
    },
    {
        prototype:
        {
            func_1: function func_1()
            {
                return 1;
            },
            func_2: function func_1()
            {
                return 2;
            }
        }
    });
})
(window, window.document, jQuery);

OR

var Device = (function(window, document, $, undefined)
{
    var DevicePrivate = function()
    {
        // constructor
    };

    DevicePrivate.prototype =
    {
        func_1: function()
        {
            return 1;
        },
        func_2: function()
        {
            return 2;
        }
    };

    return DevicePrivate;
})
(window, window.document, jQuery);

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