dom-listener

dom-listener

This library simplifies the event delegation pattern for DOM events. When you build a DOMListener with a DOM node, you can associate event handles with any of its descendant nodes via CSS selectors.

Say you have the following DOM structure.

<div class="parent">
  <div class="child">
    <div class="grandchild"></div>
    <div class="grandchild"></div>
  </div>
</div>

Now you can associate a click event with all .grandchild nodes as follows:

DOMListener = require 'dom-listener'

listener = new DOMListener(document.querySelector('.parent'))
listener.add '.grandchild', 'click', (event) -> # handle event...

Selector-Based Handlers

To create a selector-based handler, call DOMListener::add with a selector, and event name, and a callback. Handlers with selectors matching a given element will be invoked in order of selector specificity, just like CSS. In the event of a specificity tie, more recently added handlers will be invoked first.

listener.add '.child.foo', 'click', (event) -> # handler 1
listener.add '.child', 'click', (event) -> # handler 2
listener.add '.child', 'click', (event) -> # handler 3

In the example above, all handlers match an event on .child.foo, but handler 1 is the most specific, so it will be invoked first. Handlers 2 and 3 are tied in specificity, so handler 3 is invoked first since it is more recent.

Inline Handlers

To create event handlers for specific DOM nodes, pass the node rather than a selector as the first argument to DOMListener::add.

childNode = document.querySelector('.child')
listener.add childNode, 'click', (event) -> # handle inline event...

This is a bit different than adding the event handler directly via the native .addEventListener method, because only inline handlers registered via DOMListener::add will correctly interleave with selector-based handlers. Interleaving selector-based handlers with native event listeners isn't possible without monkey-patching DOM APIs because you can't ask an element what event handlers are registered.

Disposing of Handlers

If you want to remove an event handler, call .dispose() on the Disposable returned from DOMListener::add:

disposable = listener.add 'child', 'click', (event) -> # handle event
disposable.dispose() # remove event handler

Destroying the Listener

If you want to remove all event handlers associated with the listener and remove its native event listeners, call DOMListener::destroy().

listener.destroy() # All handlers are removed

You can add new event handlers and call .destroy() again at a later point.