From Joomla! Documentation


When writing a complex site with many scripts, components, plugins it is become important that every script is able to talk each other. For this Joomla! introduces Client Side event convention.

The basics[edit]

The extensions should use CustomEvent() to talk to each other and to Joomla! core. The event should be dispatched to modified Element or to window (global)

The event name should have at least two part, separated ":", eg foo:bar, myshop:add-to-cart. Where the first part is an "event supporter", and the second part is the event name which happened. Which is allow us to avoid possible collisions with another scripts and native DOM events. All Joomla! events should start from `joomla:`.

Example telling that User added something to the shopping cart:

// Shop extension:
window.dispatchEvent(new CustomEvent('myshop:add-to-cart', {
  detail: {sku:'productSku', amount:10, name: 'Foo Bar'}
  bubbles: true,
  cancelable: true

Then 3rd script can listen to it:

window.addEventListener('myshop:add-to-cart', function(event) {

List of events[edit]


Dispatch it over the changed container, after the content was changed example via ajax. Joomla listen to this event to update or initialise its scripts accordingly to new content (example in a subform field).

Example content update with AJAX:

var $someContainer = document.querySelector('.my-dinamic-container');
    .then(function(res) {
        return res.text();
    .then(function(data) {
        $someContainer.innerHTML = data;
        $someContainer.dispatchEvent(new CustomEvent('joomla:updated', {
          bubbles: true,
          cancelable: true

The extensions can listen to it also, example to do initialisation for modified part of the page:

document.addEventListener('joomla:updated', function(event){
    var $elements = event.target.querySelectorAll('.foo-bar');
    // ... do something with $elements