jQuery doesn't find dynamically added DOM objects?

Question

I am very new at jQuery ... I've used Javascript many times and am quite familiar with DOM manipulation but simply not the API or gears of jQuery.

I am dynamically adding DOM elements via a JSON call like so:

$(document).ready(function() {
        var url = "jsonMenuItems.js";
        $.getJSON(url, null, function(data) {
            var html = "";
            //alert(data.items);
            data = data.items;
            for (var key in data) {      
                html += "<td class=\"menuItem\"><span>" + data[key].name + "</span></td>";
            };
            $("#menuTR").html(html);
        });

        var lZeroArray = $("#menu td");
        lZeroArray.click(function() {
            $("#submenu").slideDown("fast");
        });
    });

If the TD items are on the page manually the click function slideDown works perfectly ... if I use the above code to dynamically add the TD items then the click function slideDown does not fire.

jQuery cannot find it's own added items or am I doing something wrong?

Answer 1

Take a look at jQuery live. This will let you bind events to dynamically added items.

$("#menu td").live("click", function(){
    $("#submenu").slideDown("fast");
});

Answer 2

It looks like you're adding the click event to the wrong elements. You're adding the dynamically added TDs to an element with id="menuTR", but you're setting the click event on TD elements that are descendants of id="menu"

To test, try changing $("#menu td") to $("#menuTR td"), or vice versa. Alternately, you could try selecting the elements with $("td.menuItem"), which selects all TD elements with a class of menuItem.

Answer 3

the problem is: your event handler is bound to $('#menu td'), but at the time that this is done, there are no tds in the #menu!

using live() makes sure that jquery adds event handlers to objects added later on to the DOM.

Alternatively, a solution used in older jquery versions would be:

    var url = "jsonMenuItems.js";
    $.getJSON(url, null, function(data) {
        var html = "";
        //alert(data.items);
        data = data.items;
        for (var key in data) {
                  html += "<td class=\"menuItem\"><span>" + data[key].name + "</span></td>";
        };
        $("#menuTR").html(html);
        $("#menu td").click(function() { 
           $("#submenu").slideDown("fast");
        });
    });
    var lZeroArray = $("#menu td");
    lZeroArray.click(function() { 
       $("#submenu").slideDown("fast");
    });

Answer 4

That is because you have to reapply the click functionality to them after they are created:

$.getJSON(url, null, function(data) {
        var html = "";
        //alert(data.items);
        data = data.items;
        for (var key in data) {      
            html += "<td class=\"menuItem\"><span>" + data[key].name + "</span></td>";
        };
        $("#menuTR").html(html);

        $("#menu td").click(function() {
            $("#submenu").slideDown("fast");
        });

    });