bootstrap 3 navbar collapse button not working

You need to change in this markup

 <button type="button" class="navbar-toggle" data-toggle="collapse" data-target=".navbar collapse">

change the

data-target=".navbar collapse"

to

data-target=".navbar-collapse"

Reason : The value of data-target is a any class name of the associated nav div. In this case it is

<div class="collapse navbar-collapse">  <-- Look at here
     <ul class="nav navbar-nav navbar-right">
     .....
</div>

Js Fiddle Demo