Highlighting current section in navbar

Question

I have a scrolling page with a navbar and I want the section the user is scrolling through to be highlighted in the navbar. At the moment it almost accomplishes this, but is highlighting the incorrect link.

A demonstration is at http://codepen.io/meek/pen/NNprYb?editors=1000

The code that does this is as follows:

// highlight current tab
    $(window).on("scroll", function() {

        var currentPos = $(window).scrollTop();

        $('.nav li a').each(function() {
            var sectionLink = $(this);
            var section = $(sectionLink.attr('href'));
            if(section.position().top <= currentPos && sectionLink.offset().top + section.height() >= currentPos) {
                $('.nav li').removeClass('active');
                sectionLink.parent().addClass('active');
            }
            else {
                sectionLink.parent().removeClass('active');
            }
        });

    });

I've tried several things, but can't get it to reliably add the active class to the correct session. Help appreciated!

edit: to be clearer, the problem is that it's only highlighting the section when you've scrolled a bit into it, instead of right at the top, meaning that when you click a section to scroll to the top of that section automatically, that section is not highlighted.

edit2: So changing the if statement to:

if(currentPos + $('#nav-wrapper').outerHeight() >= section.position().top && currentPos + $('#nav-wrapper').outerHeight() <= sectionLink.offset().top + section.outerHeight()) {

has made an improvement although not completely fixed the issue. The home, about and portfolio sections all highlight the correct link but not contact.

Answer 1

You need to account for the height of the navbar and subtract it from the top of the section you want highlighted.

The height is currently hardcoded in your CSS at 75px but I included a jQuery selector for the height in case it needs to change/disappear for smaller screens.

Nice work by the way.

$(window).on("scroll", function() {
  var currentPos = $(window).scrollTop();

  $('.nav li a').each(function() {
    var sectionLink = $(this);
    // capture the height of the navbar
    var navHeight = $('#nav-wrapper').outerHeight() + 1;
    var section = $(sectionLink.attr('href'));

    // subtract the navbar height from the top of the section
    if(section.position().top - navHeight  <= currentPos && sectionLink.offset().top + section.height()> currentPos) {
      $('.nav li').removeClass('active');
      sectionLink.parent().addClass('active');
    } else {
      sectionLink.parent().removeClass('active');
    }
  });        
});