Need help building a jQuery dropdown menu

Question

Hi folks

I'm just starting out with jQuery. I want to make a simple 'ul' dropdown menu to improve my understanding. The basic flow is this:

'ul.menu li ul' has display:none >> on hover of li, get & store height of 'this' ul >> set height of 'this' ul to 0 >> set display to block >> animate height to original stored height

I know there are already some great plugins for dropdowns, but I really want to roll my own to get a better understanding of jQuery.

So far I have managed the following, very badly done (see live version here - http://jsbin.com/eduvi):

---

var $j = jQuery.noConflict();
$j(document).ready(function(){

// Get height of current hidden ul

        $j("ul.menu li").hover(function() { 
          getHeight($j("ul", this).height()); 
        });
// Set height to 0px    

    $j('ul.menu li').hover(function() { 
    $j("ul", this).css({"height":"0px"});
});

// Set display to block 

    $j('ul.menu li').hover(function() { 
    $j("ul", this).css({"display":"block"});
});

// Animate height to stored height  

    $j('ul.menu li').hover(function getHeight(h) { 
    $j('ul:first', this).stop().animate({ "height" : "100%" } , 400 );
});

// Display height of current hidden ul

    function getHeight(h) {
      $j("div.test").text("The height for the hidden ul is " + h + "px."); }
  });

---

I'd like to know how do I get it to use the stored original height, in place of that 100%.

And secondly, I'm sure this can all be condensed down to just a few lines, but don't really have a clue how to do that yet.

Any help very much appreciated!

UPDATE: OK, so I'm ALMOST there. I used the code Marve posted as a base and worked in the other bits. The only thing that's not working is I need to reset the height of the hidden UL, at the end of everything, to it's original height, and set it's display to none, so it's ready to be hovered again. Any ideas why it won't work?

---

$j('ul.menu > li').hover(
    function() { var ulHeight = $j('ul', this).height(); $j(this).children('ul').css({height: 0}).stop().animate({height: ulHeight}, 400); },
    function() { $j(this).children('ul').stop().animate({height: 0}, 400).css({height: ulHeight, display:none});   }
);

---

Answer 1

here's a simple css tip to help you:

use $('ul.menu > li') instead of just$('ul.menu li')

This will make the hover only target the menu under the list item you are hovering over.

Answer 2

It's great that you're learning jQuery and using this problem to do it. Kudos for that!

I think you're over-engineering the solution to the problem. Take a look at two built-in jQuery functions that help remove some of the effort from the solution: slideDown and slideUp. You'll undoubtedly find many more helpful functions in the jQuery documentation. This snippet of code does much of what you posted already:

$j(document).ready(function() {
    $j('ul.menu > li').hover(
        function() { $j(this).children('ul').stop(true, true).slideDown(); },
        function() { $j(this).children('ul').stop(true, true).slideUp(); }
    );
});

The snippet doesn't handle the sub menus you have in your HTML sample, but given your desire to learn, it shouldn't be a stretch to implement it.

Also see the docs on stop.