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up vote 5 down vote favorite
1

In my latest code, I have an event handler for a focus on a textarea. When the user clicks on the textarea, that event-handler is triggered which sets some other DOM states based on the selected textarea. However, elsewhere in my program I want to programmatically set the focus of the textarea without triggering that event handler. I know Backbone, for instance, has a way to silently perform an action.

My only pseudo-solution is to temporarily set a variable:

var silence = true;

And then, in my event handler, only perform the logic if silence is false. The handler is still triggered, but the logic doesn't run.

Does anyone else know of better strategies for this?

share|improve this question
    
What are you using to bind events, jQuery? –  Glenn Slaven Oct 25 '12 at 23:35
    
I'm actually using Meteor github.com/meteor/meteor for this particular project, so I was primarily interested in vanilla JS solutions, but jQuery ones are good, too. –  bento Oct 26 '12 at 0:12

3 Answers 3

up vote 2 down vote accepted 
<input type="text" name="input" id="input" value="0">
<input type="text" name="input" id="input2" value="0">

<script src="http://ajax.googleapis.com/ajax/libs/jquery/1.8.2/jquery.min.js" type="text/javascript"></script>
<script>
$(function() {

$('#input').focus(function(a,b) {
   if (b) alert('forced');
});

$('#input').trigger('focus', jQuery.Event("focus"));

});
</script>

When b argument of the event handler is present, the event is triggered by invoking $('#input').trigger('focus', jQuery.Event("focus"));. So you can make you handler function execute depending on normal focus or forced focus.

share|improve this answer
    
Very elegant solution, I like it! –  Glenn Slaven Oct 25 '12 at 23:46
    
Not documented but works anyway. –  Reflective Oct 25 '12 at 23:48
    
Not documented? This is the use of extraParameters in api.jquery.com/trigger. Why not simply passing true instead of weird jQuery.Event("focus")? –  Pierre Dec 21 '12 at 9:53
up vote 3 down vote

You could temporarily unbind() the event, like this:

You have the following scenario where you handle the focus event:

function focus_handler() {
   //focus handler code
   ...
   ...
}

$('#yourelement').bind('focus', focus_handler);

And now on the part of the code where you want to programmatically focus the element without triggering the event handler:

$('#yourelement').unbind('focus');
$('#yourelement').focus();
$('#yourelement').bind('focus', focus_handler);
share|improve this answer
up vote 1 down vote

In jQuery, trigger() can take an event namespace. Only events bound with this namespace, and default behaviour, will be triggered.

So for example:

$('#yourelement').trigger('focus.anyOldNonsense');

should do the trick (provided no-one has used "anyOldNonsense" as an event namespace).

Edit: This works in 1.7.2 and 1.8.3, but there is a known bug in 1.9 onwards for adding data and namespaces to a "focus" event.

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