Hide Twitter Bootstrap nav collapse on click

try this:

$('.nav a').on('click', function(){
    $('.btn-navbar').click(); //bootstrap 2.x
    $('.navbar-toggle').click(); //bootstrap 3.x by Richard
    $('.navbar-toggler').click(); //bootstrap 4.x
});

I just replicate the 2 attributes of the btn-navbar (data-toggle="collapse" data-target=".nav-collapse.in") on each link like this:

<div class="nav-collapse">
  <ul class="nav" >
    <li class="active"><a href="#home" data-toggle="collapse" data-target=".nav-collapse.in">Home</a></li>
    <li><a href="#about" data-toggle="collapse" data-target=".nav-collapse.in">About</a></li>
    <li><a href="#portfolio" data-toggle="collapse" data-target=".nav-collapse.in">Portfolio</a></li>
    <li><a href="#services" data-toggle="collapse" data-target=".nav-collapse.in">Services</a></li>
    <li><a href="#contact" data-toggle="collapse" data-target=".nav-collapse.in">Contact</a></li>
  </ul>
</div>

In the Bootstrap 4 Navbar, in has changed to show so the syntax would be:

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

$(function() {
    $('.nav a').on('click', function(){ 
        if($('.navbar-toggle').css('display') !='none'){
            $('.navbar-toggle').trigger( "click" );
        }
    });
});

Better to use default collapse.js methods (V3 docs, V4 docs):

$('.nav a').click(function(){
    $('.nav-collapse').collapse('hide');
});