Problem calling method inside another method in javascript?

Question

Hi, I am having a JavaScript namespace say

A={

  CA: function()
  {
    this.B();
  },

  B: function()
  {
    var test='test';
    var result='t1';

    C: function()
    {
      this.test='test1';
      .....
      .....
      return 'test1';    
    }

   result=this.C();  
   return result; 
  }
}

Now when I am executing such code it is giving that TypeError: this.C is not a function. Can somebody tell me why it is so. I know it is something related with lexical scoping but am unable to understand this.

Answer 1

I think the problem is that when this.C() is executed inside the function referred to by B, this refers to the object that contains B, that is, object A. (This assumes B() is called within the context of A)

The problem is, C does not exist on the object A, since it's defined within B. If you want to call a local function C() within B, just use C().

EDIT: Also, I'm not sure what you've posted is valid JavaScript. Specifically, B should be defined this way, since you can't use the object:property syntax within a function.

B: function()
{
  var test='test';
  var result='t1';

  var C = function()
  {
    this.test='test1';
    return 'test1';    
  }

 result=C();  
 return result; 
}

Answer 2

I am actually surprised that your code doesn't give you error on the 'C:' line.

Anyway, your syntax to define a function is not correct. Define it using the var keyword. Also, notice that I created the 'closure' so that the function C can access 'this'. See the code below:

A={

  CA: function()
  {
    this.B();
  },

  B: function()
  {
    var test='test';
    var result='t1';

    var self = this;
    var C = function()
            {
              self.test='test1';
              .....
              .....
              return 'test1';    
            }

   result=C();
   return result; 
  }
}

If you want to assign C to 'this' object, you can also do:

A={

  CA: function()
  {
    this.B();
  },

  B: function()
  {
    var test='test';
    var result='t1';

    var self = this;
    this.C = function()
             {
              self.test='test1';
              .....
              .....
              return 'test1';    
             };

   result= this.C();
   return result; 
  }
}

Answer 3

You have to be careful when you use this to identify anything in Javascript because each time you change scope "this" changes.

Assigning the 'this' reference to it's own variable helps get around this.

var a = new function() {
    var self = this;

    self.method = function() { alert('hiya'); };

    var b = function() {
        this.method(); // this isn't 'a' anymore?
        self.method(); // but 'self' is still referring to 'a'
    };

};