javascript object oriented call function inside function or call function insede var

Question

i try to understand javascript now what i really want to achieve is something like this :

var data = Data.GetData();//with or without parameter Data.GetData(x)
//or
var data = Data.Row.GetData();

what i understand from other oop languange i just create class like this :

Class Data{
  public static String GetData()
  {
     return "data";
  }
}

So I can call :

String data = Data.GetData();
//or
Data _data = new Data();
String x = _data.GetData();

but how in javascript? i think like this :

function Data(){
  function GetData(){
    retun "data";
  }
}

but it didn't work. :( please help me understand oop how to make this in javascript, with example code :D

Joe Minichino · Accepted Answer · 2013-11-29 10:39:34Z

5

In javascript you can declare a function as a constructor (by making sure it doesn't return anything) and then have methods for that class applied to all its instances by using prototypal inheritance.

function Data () {
}
Data.prototype.GetData = function () {
  return 'data';
}

you can then use it like so:

var data = new Data();
var str = data.GetData();

if you want a static method you can omit the prototype keyword

Data.GetData = function () { return 'data'; }

If instead your Data object is a single object and you don't want to reuse any of its methods and members you can simply declare it like this:

var Data = {
  GetData: function () { return 'data'; }
};

and then do

Data.GetData();

answered Nov 29, 2013 at 10:39

Joe Minichino

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Comments

Luca Rainone · Accepted Answer · 2013-11-29 10:39:47Z

2

Data is a simple Object, and GetData is a key with function as value

var Data = {
    GetData: function() {
           return "data";
     }
}

in the second case:

var Data = {
    Row: {
         GetData: function() {
               return "data";
         }
    }
}

answered Nov 29, 2013 at 10:39

Luca Rainone

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Comments

T.J. Crowder · Accepted Answer · 2013-11-29 10:39:33Z

Functions in JavaScript are first class objects. "Methods" are just properties on objects that point to functions. The act of calling the function via a property reference is a bit special, in that it sets the meaning of this within the call to the function (this is set to the object the property was on). Unlike some other languages you may be used to, that is a runtime thing decided by how the function is called, not a compile-time thing decided by where the function is declared/defined.

To be able to do this:

var data = Data.GetData();

...you need to have an object, Data, that has a property called GetData that refers to a function. You can build that like this:

var Data = {
    GetData: function() {
        // ...your code here...
    }
};

...or any of several other ways, such as:

var Data = {};
Data.GetData = function() {
    // ...your code here...
};

...or

var Data = {};
Data.GetData = GetData;
function GetData() {
    // ...your code here...
}

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