Programmatically toggle bootstrap 3 navigation bar

As you said, the event will run a modal.

So, when your modal ( called yourModal ) is showing (before showing), just hide the menu :

JS :

$('.yourModal').on('show.bs.modal', function(){
    $('.navbar-collapse').collapse('hide');
});

Here are the docs :

http://getbootstrap.com/javascript/#collapse

http://getbootstrap.com/javascript/#modals-usage

After a little bit of help from @Jahnux73 I figured it out myself. So the only thing I had to do is to add :

data-toggle="collapse" data-target=".navbar-ex1-collapse"

to the specific link that I wanted to toggle the navbar. so the link now looks like following:

<a href="#" id="online-offline" data-toggle="collapse" 
   data-target=".navbar-ex1-collapse" toggle="offline">
    <span class="glyphicon glyphicon-off"></span>&nbsp;Go offline
</a>