[javascript] Event binding on dynamically created elements?


Answers

There is a good explanation in the documentation of jQuery.fn.on.

In short:

Event handlers are bound only to the currently selected elements; they must exist on the page at the time your code makes the call to .on().

Thus in the following example #dataTable tbody tr must exist before the code is generated.

$("#dataTable tbody tr").on("click", function(event){
    console.log($(this).text());
});

If new HTML is being injected into the page, it is preferable to use delegated events to attach an event handler, as described next.

Delegated events have the advantage that they can process events from descendant elements that are added to the document at a later time. For example, if the table exists, but the rows are added dynamically using code, the following will handle it:

$("#dataTable tbody").on("click", "tr", function(event){
    console.log($(this).text());
});

In addition to their ability to handle events on descendant elements which are not yet created, another advantage of delegated events is their potential for much lower overhead when many elements must be monitored. On a data table with 1,000 rows in its tbody, the first code example attaches a handler to 1,000 elements.

A delegated-events approach (the second code example) attaches an event handler to only one element, the tbody, and the event only needs to bubble up one level (from the clicked tr to tbody).

Note: Delegated events do not work for SVG.

Question

I have a bit of code where I am looping through all the select boxes on a page and binding a .hover event to them to do a bit of twiddling with their width on mouse on/off.

This happens on page ready and works just fine.

The problem I have is that any select boxes I add via Ajax or DOM after the initial loop won't have the event bound.

I have found this plugin (jQuery Live Query Plugin), but before I add another 5k to my pages with a plugin, I want to see if anyone knows a way to do this, either with jQuery directly or by another option.




Event binding on dynamically created elements

Single element:

$(document.body).on('click','.element', function(e) {  });

Child Element:

 $(document.body).on('click','.element *', function(e) {  });

Notice the added *. An event will be triggered for all children of that element.

I have noticed that:

$(document.body).on('click','.#element_id > element', function(e) {  });

It is not working any more, but it was working before. I have been using jQuery from Google CDN, but I don't know if they changed it.




Try to use .live() instead of .bind(); the .live() will bind .hover to your checkbox after the Ajax request executes.




I prefer using the selector and I apply it on the document.

This binds itself on the document and will be applicable to the elements that will be rendered after page load.

For example:

$(document).on("click", $(selector), function() {
    // Your code here
});



<html>
    <head>
        <title>HTML Document</title>
        <script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/1.12.0/jquery.min.js"></script>
    </head>

    <body>
        <div id="hover-id">
            Hello World
        </div>

        <script>
            jQuery(document).ready(function($){
                $(document).on('mouseover', '#hover-id', function(){
                    $(this).css('color','yellowgreen');
                });

                $(document).on('mouseout', '#hover-id', function(){
                    $(this).css('color','black');
                });
            });
        </script>
    </body>
</html>



Any parent that exists at the time the event is bound and if your page was dynamically creating elements with the class name button you would bind the event to a parent which already exists

$(document).ready(function(){
  //Particular Parent chield click
  $(".buttons").on("click","button",function(){
    alert("Clicked");
  });  
  
  //Dynamic event bind on button class  
  $(document).on("click",".button",function(){
    alert("Dymamic Clicked");
  });
  $("input").addClass("button");  
});
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script>
<div class="buttons">
  <input type="button" value="1">
  <button>2</button>
  <input type="text">
  <button>3</button>  
  <input type="button" value="5">  
  </div>
<button>6</button>



More flexible solution to create elements and bind events (source)

// creating a dynamic element (container div)
var $div = $("<div>", {id: 'myid1', class: 'myclass'});

//creating a dynamic button
 var $btn = $("<button>", { type: 'button', text: 'Click me', class: 'btn' });

// binding the event
 $btn.click(function () { //for mouseover--> $btn.on('mouseover', function () {
    console.log('clicked');
 });

// append dynamic button to the dynamic container
$div.append($btn);

// add the dynamically created element(s) to a static element
$("#box").append($div);

Note: This will create an event handler instance for each element (may affect performance when used in loops)




You can add events to objects when you create them. If you are adding the same events to multiple objects at different times, creating a named function might be the way to go.

var mouseOverHandler = function() {
    // Do stuff
};
var mouseOutHandler = function () {
    // Do stuff
};

$(function() {
    // On the document load, apply to existing elements
    $('select').hover(mouseOverHandler, mouseOutHandler);
});

// This next part would be in the callback from your Ajax call
$("<select></select>")
    .append( /* Your <option>s */ )
    .hover(mouseOverHandler, mouseOutHandler)
    .appendTo( /* Wherever you need the select box */ )
;



Take note of "MAIN" class the element is placed, for example,

<div class="container">
     <ul class="select">
         <li> First</li>
         <li>Second</li>
    </ul>
</div>

In the above scenario, the MAIN object the jQuery will watch is "container".

Then you will basically have elements names under container such as ul, li, and select:

$(document).ready(function(e) {
    $('.container').on( 'click',".select", function(e) {
        alert("CLICKED");
    });
 });



Try like this -

$(document).on( 'click', '.click-activity', function () { ... });





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