Javascript-从名称空间回调函数问题？

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

Answer 1

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/

Answer 2

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);
 };