A simple mega menu implementation with CSS and jquery

I’ve been skinning quite a few ecommerce sites with the magento platform and wanted a simple way to explode the navigation menus. Some sites end up getting a long list of categories and sub-categories, so I wanted to do a mega-menu style navigation. One way to do it was to rewrite the html code for the navigation and pop each column into another nested unordered list. I’m not a fan of doing this because one – I didn’t want to manipulate the html. I like the simplicity of ul navigation with a clear flat list of li elements. Of course for nested sub-navigation any li can contain another ul. I wanted to just use some css and maybe javascript to visually accomplish the same thing. I also wanted it to be portable, so I could take it and use it on a wordpress install or even a plain html site. I went to my favorite: jquery. I knew there was a likely plugin out there already that would do something similar, but nothing after my initial search, but I realized that it was a simple procedure and mostly accomplished with some css.

I’ll walk you through the process here and let you inspect the code yourself and see it in action on the demo page. Assign each ul to be a default width of 15em, then each li element we float:left and also give it a width of 15em. This way we can change the ul width to 30em and automatically I have 2 columns! Assigning the nested ul a specific width according to it’s class is done through css, mm-0 will be 15em and incrementally each next one will be 15em more. mm-1 is 30 and mm-2 is 45. Then we use jquery to determine the number of elements in the list and assign it a class accordingly. This involves some math and some preferences. Using the magic ui number 7, I determined that a menu with more than 7 elements should explode into multiple columns. So anything less than or equal to 7 I assign the class ‘mm-1′ which in the css sets the width to the standard 15em (ie 1 mega menu column). More than 7 should pop into columns no more than 8 tall. So dividing the total by 8 will give us the number of columns we want. We’ll add a class of mm-x, where x would be the number of columns. And the li elements will float to the left and fill in the space in columns.
One specific issue is the last element in the menu, sometimes we need to style that element differently. I’ll loop through each child of the nested ul element and if it is on the bottom row apply a class of ‘last’. But this was a little tricky in calculating which would be last because were never sure how many elements there will be or how many columns. I just used the remainder after dividing the total by the number of columns, then if the remainder could be used to know which elements are on the bottom row.

OK, now that that’s out of the way, let’s look at the code.

HTML

This I won’t show, you can inspect the source of the demo if you wish to see it, it a basic nested collection of unordered lists. It’s the standard that is created by magento, wordpress and most other CMS platforms.

CSS

Javascript

Don’t forget to include jQuery (I prefer using the google hosted version at http://ajax.googleapis.com/ajax/libs/jquery/1.4.2/jquery.min.js)

See the demo in action