For Bootstrap 3:
var url = window.location;
// Will only work if string in href matches with location
$('ul.nav a[href="'+ url +'"]').parent().addClass('active');
// Will also work for relative and absolute hrefs
$('ul.nav a').filter(function() {
return this.href == url;
}).parent().addClass('active');
For Bootstrap 4:
var url = window.location;
// Will only work if string in href matches with location
$('ul.navbar-nav a[href="'+ url +'"]').parent().addClass('active');
// Will also work for relative and absolute hrefs
$('ul.navbar-nav a').filter(function() {
return this.href == url;
}).parent().addClass('active');