jQuery & jQuery UI Documentation

jQuery & jQuery UI

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.trigger()

Categories: Events > Event Handler Attachment

.trigger( eventType, extraParameters ) Returns: jQuery

Description: Execute all handlers and behaviors attached to the matched elements for the given event type.

  • version added: 1.0.trigger( eventType, extraParameters )

    eventTypeA string containing a JavaScript event type, such as click or submit.

    extraParametersAdditional parameters to pass along to the event handler.

  • version added: 1.3.trigger( event )

    eventA jQuery.Event object.

Any event handlers attached with .bind() or one of its shortcut methods are triggered when the corresponding event occurs. They can be fired manually, however, with the .trigger() method. A call to .trigger() executes the handlers in the same order they would be if the event were triggered naturally by the user:

$('#foo').bind('click', function() {
      alert($(this).text());
    });
    $('#foo').trigger('click');

As of jQuery 1.3, .trigger()ed events bubble up the DOM tree; an event handler can stop the bubbling by returning false from the handler or calling the .stopPropagation() method on the event object passed into the event. Although .trigger() simulates an event activation, complete with a synthesized event object, it does not perfectly replicate a naturally-occurring event.

To trigger handlers bound via jQuery without also triggering the native event, use .triggerHandler() instead.

When we define a custom event type using the .bind() method, the second argument to .trigger() can become useful. For example, suppose we have bound a handler for the custom event to our element instead of the built-in click event as we did above:

$('#foo').bind('custom', function(event, param1, param2) {
  alert(param1 + "\n" + param2);
});
$('#foo').trigger('custom', ['Custom', 'Event']);

The event object is always passed as the first parameter to an event handler, but if additional parameters are specified during a .trigger() call, these parameters will be passed along to the handler as well. To pass more than one parameter, use an array as shown here. As of jQuery 1.6.2, a single parameter can be passed without using an array.

Note the difference between the extra parameters we're passing here and the eventData parameter to the .bind() method. Both are mechanisms for passing information to an event handler, but the extraParameters argument to .trigger() allows information to be determined at the time the event is triggered, while the eventData argument to .bind() requires the information to be already computed at the time the handler is bound.

Examples:

Example: Clicks to button #2 also trigger a click for button #1. 

<!DOCTYPE html>
<html>
<head>
  <style>

button { margin:10px; }
div { color:blue; font-weight:bold; }
span { color:red; }
</style>
  <script src="http://code.jquery.com/jquery-1.7rc2.js"></script>
</head>
<body>
  <button>Button #1</button>
<button>Button #2</button>
<div><span>0</span> button #1 clicks.</div>

<div><span>0</span> button #2 clicks.</div>
<script>
$("button:first").click(function () {
update($("span:first"));
});
$("button:last").click(function () {
$("button:first").trigger('click');

update($("span:last"));
});

function update(j) {
var n = parseInt(j.text(), 10);
j.text(n + 1);
}
</script>

</body>
</html>

Example: To submit the first form without using the submit() function, try: 

$("form:first").trigger("submit")

Example: To submit the first form without using the submit() function, try: 

var event = jQuery.Event("submit");
$("form:first").trigger(event);
if ( event.isDefaultPrevented() ) {
// Perform an action...
}

Example: To pass arbitrary data to an event: 

$("p").click( function (event, a, b) {
// when a normal click fires, a and b are undefined
// for a trigger like below a refers to "foo" and b refers to "bar"

} ).trigger("click", ["foo", "bar"]);

Example: To pass arbitrary data through an event object: 

var event = jQuery.Event("logged");
event.user = "foo";
event.pass = "bar";
$("body").trigger(event);

Example: Alternative way to pass data through an event object: 

$("body").trigger({
type:"logged",
user:"foo",
pass:"bar"

});
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