adding class on a random list item

Question

I have an unordered list with list items. I have a class called 'active', which I want randomly be added on a list item. I now have this:

// I want this class added on a random list item
$("#gallery li:first-child").addClass("on"); 

Math.random?

Answer 1

var random = Math.floor(Math.random() * 1000);

var $li = $("#gallery li");
$li.eq(random % $li.length).addClass("on");

Answer 2

Try something like below,

var $li = $('#gallery li');
$li.eq(Math.floor(Math.random()*$li.length)).addClass("on");

Edit: Updated to avoid re-query DOM for li