The other day I was was trying to DRY up the code in a rails application I was working on by reusing a view that’s not a partial. I took care of the models to display in the controller but needed to show which link was active by adding the CSS class current.

My first thought was to pass something, say a hash called @link_class with possible links, through the controller.

def show
  @user = User.find(params[:id])
  @stuff = @user.stuff
  @link_class = {}
  @link_class[:my_stuff] = 'current'

def show_liked_stuff
  @user = User.find(params[:id])
  @stuff = @user.liked_stuff
  @link_class = {}
  @link_class[:likes] = 'current'
  render :show

And in my view…

<li><%= link_to 'Likes', user_liked_stuff_path(@user), class: @link_class[:likes] %></li>
<li><%= link_to 'My Stuff', user_path(@user), class: @link_class[:my_stuff] %></li>

But that left a terrible taste in my mouth. I knew it wasn’t the beer I was drinking, so I set out to craft a more elegant solution. 🍺

JavaScript has some nifty ways to grab the current URL such as window.location.href and window.location.pathname. The former will grab the entire URL while the latter will just grab the path after the protocol and domain. Pathname is what I was looking for since in my rails app I have mostly relative links to navigate around. So now I was thinking that I could somehow match the current pathname with the link and add the class I needed.

Good thing for me, jQuery can select elements by attribute and value. I can add the class for the parent element user-nav to my selector to make sure I don’t grab a link from my header or elsewhere.

$('.user-nav [href="' + window.location.pathname + '"]')

I slapped that into the console in Firefox dev tools…it works! Now I just have to add the class I need. I can use className from plain old JavaScript to do that!

$('.user-nav [href="' + window.location.pathname + '"]').className = "current";

Eureka! But what if I want to reuse this with a different nav? How about a function?

function setNavLinkClassToCurrent(navClass) {
  $(navClass + ' [href="' + window.location.pathname + '"]').className = "current";

Now we’re talking! I can reuse this puppy by just calling setNavLinkClassToCurrent('.user-nav'), setNavLinkClassToCurrent('.main-nav'), or setNavLinkClassToCurrent('.beer-nav'). I could even go a step further if we wanted to have our pick of CSS classes to apply.

function setCurrentNavLinkClass(navClass, linkClass) {
  $(navClass + ' [href="' + window.location.pathname + '"]').className = linkClass;

Cool! I can do setCurrentNavLinkClass('.user-nav', 'current') or setCurrentNavLinkClass('.main-nav', 'bananas') or whatever else floats my boat.