Javascript- Callback function issue from namespace?

Question

var myNamespace = {
    dateController: {}
};

myNamespace.dateController = function(callback) {
    this.callbackfunction = callback;
    try {
        [this.callbackfunction]();
    } catch (e) {
        alert(e);
    }
};

function displayDate() {
    alert("displayDate");
    myNamespace.dateController("displayDateFromController");
};

function displayDateFromController() {
    alert("In displayDateFromController");
};

This piece of code is giving me TypeError: ["displayDateFromController"] is not a function error. What could be root cause and possible solution to this issue.

Why dateController not able to identify displayDateFromController as function.

I have tired this on http://www.w3schools.com/js/tryit.asp?filename=tryjs_events

several issues: 1) leave out the []. What you are actually doing is putting this.callbackfunction in an array and trying to call that array as a function. 2) don't pass the functionName as a string to your dateController function. Instead just pass the function itself: myNamespace.dateController(displayDateFromController); — basilikum
– basilikum, Commented Jun 3, 2013 at 8:38
I have tired out that also... this.callbackfunction() still giving me same error. — harshit2811
– harshit2811, Commented Jun 3, 2013 at 8:41

Kevin Bowersox · Accepted Answer · 2013-06-03 09:56:30Z

2

You need to pass the actual function to the datecontroller method instead of the String.

var myNamespace = {
    dateController: {}
};

myNamespace.dateController = function (callback)
{
 this.callbackfunction = callback;
 try{
    //remove [] surrounding function
    this.callbackfunction();
    }
    catch(e)
    {
      alert(e);
    }
};

//Declare this method prior to displayDate
function displayDateFromController()
{
    alert("In displayDateFromController");
};

function displayDate()
{
    alert("displayDate");
    //Pass function instead of string
    myNamespace.dateController(displayDateFromController); 
};

displayDate();

Working Example: http://jsfiddle.net/RDMHV/

If you still need the flexibility of a String:

var myNamespace = {
    dateController: {}
};

myNamespace.dateController = function (callback)
{
 this.callbackfunction = this[callback];
 try{
    this.callbackfunction();
    }
    catch(e)
    {
      alert(e);
    }
};

myNamespace.displayDateFromController = function(){
   alert("In displayDateFromController");
};

function displayDate()
{
    alert("displayDate");
    myNamespace.dateController("displayDateFromController");
};

displayDate();

Working Example http://jsfiddle.net/RDMHV/1/

edited Jun 3, 2013 at 9:56

answered Jun 3, 2013 at 8:44

Kevin Bowersox

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2 Comments

harshit2811 Over a year ago

thanks @Kevin for prompt reply... I can relate your answer with function pointer fundamental. I know that but in this case i have some specific requirement in which i have to keep function name in string. Will it possible to still passing function name as string and calling the same from controller.

harshit2811 Over a year ago

Is it necessary to have displayDateFromController in myNamespace in your second codebase? can't i have similar to displayDate? Actually i am relating this issue with global namespace and myNamespace scope issue. displayDateFromController is part of globale namespace thats why it is not detecting function from string.

Samuel Caillerie · Accepted Answer · 2013-06-03 08:42:12Z

0

You have to remove the brackets around the call :

try{
    this.callbackfunction();
}
catch(e)
{
    alert(e);
}

and to pass the function without the quotes :

function displayDate()
{
    alert("displayDate");
    myNamespace.dateController(displayDateFromController);
 };

answered Jun 3, 2013 at 8:42

Samuel Caillerie

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