How can I pass a variable parameter to an anonymous function using jquery?

Question

Can someone tell me what I am doing wrong here? I simplified it below but I am basically trying to create a list and have a click event that references a variable only available in the loop.

for (var i = 0; i < data.length; i++) {                                                                           
  $newRow = $(rowFormat);                    
  $('a:first', $newRow).click(function(i){
    return function() { alert(i); } 
  });
  $list.append($newRow);      
}

Answer 1

You aren't calling the outer function.

$('a:first', $newRow).click(function(j){
  return function() { alert(j); } 
}(i)); /* Pay special attention to this line, it is where the major change is */

As TJ Crowder mentioned, you can move the factory out of the loop.

function my_factory(j) {
    return function() { 
        alert(j); 
    }; 
}

$('a:first', $newRow).click(my_factory(i));

Answer 2

You've almost got it, just one small change. This is actually my favorite example of a practical use of a closure in Javascript.

Basically, you need to create a function that takes a value, and returns a function that uses that value. See the commented line below for what your example is missing. Your code created the anonymous function, but didn't invoke it.

for (var i = 0; i < data.length; i++) {                                                                           
  $newRow = $(rowFormat);
  var fn = (function (value) {
    return function() {
      alert(value);
    };
  }) (i); //this is what you were missing, you need to invoke the anonymous function
  $('a:first', $newRow).click(fn);
  $list.append($newRow);      
}

Answer 3

Use 'bind' to attach the 'click' event and pass a parameter. Using 'event.data' you will be able to get the right value of your parameter:

Example 1:

 $(document).ready(function()
 {
    for (var i = 0; i < data.length; i++) 
    {                                                                           
        $newRow = $(rowFormat);                    
        $('a:first', $newRow).bind('click', {i: i},
            function (event)
            {
                alert(event.data.i);
            }
        );
        $list.append($newRow);      
    }
});

Example 2:

$(document).ready(function()
{
    $(".selectorA").each(function()
    {
        var elementId = $(this).attr("id");

        for(var i = 0; i < 20; i++) 
        {
            $('#question' + i).bind('click', {currentIndex: i, elementId: elementId}, 
                function (event)
                {
                   alert(event.data.currentIndex + " | " + event.data.elementId);
                }
            );
        }
    }
});