jQuery: more than one handler for same event

What happens if I bind two event handlers to the same event for the same element?

For example:

var elem = $("...")
elem.click(...);
elem.click(...);

Does the last handler "win", or will both handlers be run?

Solution 1:

Both handlers will run, the jQuery event model allows multiple handlers on one element, therefore a later handler does not override an older handler.

The handlers will execute in the order in which they were bound.

Solution 2:

Suppose that you have two handlers, f and g, and want to make sure that they are executed in a known and fixed order, then just encapsulate them:

$("...").click(function(event){
  f(event);
  g(event);
});

In this way there is (from the perspective of jQuery) only one handler, which calls f and g in the specified order.

Solution 3:

jQuery's .bind() fires in the order it was bound:

When an event reaches an element, all handlers bound to that event type for the element are fired. If there are multiple handlers registered, they will always execute in the order in which they were bound. After all handlers have executed, the event continues along the normal event propagation path.

Source: http://api.jquery.com/bind/

Because jQuery's other functions (ex. .click()) are shortcuts for .bind('click', handler), I would guess that they are also triggered in the order they are bound.

Solution 4:

You should be able to use chaining to execute the events in sequence, e.g.:

$('#target')
  .bind('click',function(event) {
    alert('Hello!');
  })
  .bind('click',function(event) {
    alert('Hello again!');
  })
  .bind('click',function(event) {
    alert('Hello yet again!');
  });

I guess the below code is doing the same

$('#target')
      .click(function(event) {
        alert('Hello!');
      })
      .click(function(event) {
        alert('Hello again!');
      })
      .click(function(event) {
        alert('Hello yet again!');
      });

Source: http://www.peachpit.com/articles/article.aspx?p=1371947&seqNum=3

TFM also says:

When an event reaches an element, all handlers bound to that event type for the element are fired. If there are multiple handlers registered, they will always execute in the order in which they were bound. After all handlers have executed, the event continues along the normal event propagation path.

Solution 5:

Both handlers get called.

You may be thinking of inline event binding (eg "onclick=..."), where a big drawback is only one handler may be set for an event.

jQuery conforms to the DOM Level 2 event registration model:

The DOM Event Model allows registration of multiple event listeners on a single EventTarget. To achieve this, event listeners are no longer stored as attribute values