jQuery 'on' not registering in dynamically generated modal popup

Question

I was under the impression that jQuery's on event handler was meant to be able to 'listen' for dynamically created elements AND that it was supposed to replace the behavior of live. However, what I have experienced is that using on is not capturing the click event whereas using live is succeeding!

The tricky aspect of my situation is that I am not only dynamically creating content but I'm doing it via an AJAX .get() call, and inserting the resultant HTML into a modal .dialog() jQueryUI popup.

Here is a simplified version of what I was trying to accomplish (wrapped in $(document).ready(...) ):

$.get("getUserDataAjax.php", queryString, function(formToDisplay) {
    $("#dialog").dialog({
        autoOpen: true,
        modal: true,
        buttons...
    }).html(formToDisplay);
});
$(".classThatExistsInFormToDisplay").on("click", function() {
    alert("This doesn't get called");
});

From the documentation for on I found this which which was how I was approaching writing my on event:

$("p").on("click", function(){
    alert( $(this).text() );
});

However, for some reason, live will work as I expect -- whereas on is failing me.

This isn't a question for "how can I make it work" because I have found that on will succeed (capture clicks) if I declare it inside the function(formToDisplay) callback.

My question is: what is wrong with on that it isn't finding my dynamically created elements within a modal popup? My jQuery instance is jquery-1.7.2. jQueryUI is 1.8.21.

Here are two jsFiddles that approximate the issue. Click the word "Test" in both instances to see the different behavior. The only difference in code is replacing on for live.

Where the click is captured by live.

Where the click is NOT captured by on (click 'Test - click me' to see nothing happen).

I realize I may just be using on inappropriately or asking it to do something that was not intended but I want to know why it is not working (but if you have something terribly clever, feel free to share). Thanks for your wisdom!

Update / Answer / Solution:

According to user 'undefined', the difference is that on is not delegated all the way from the top of the document object whereas live does/is.

As Claudio mentions, there are portions of the on documentation that reference dynamically created elements and that what you include in the $("") part of the query needs to exist at runtime.

Here is my new solution: Capture click events on my modal dialog, which, although it does not have any content when the event is created at runtime, will be able to find my content and element with special class that gets generated later.

$("#dialog").on("click", ".classThatExistsInFormToDisplay", function() {
    ... //(success! Event captured)
});

Thanks so much!

Answer 1

live delegates the event from document object, but on doesn't, if you want to delegate the event using on method, you should delegate the event from one of static parents of the element or document object:

$(document).on("click", ".clickHandle", function() {
    alert("Content clicked");
});