Question

How can I use jQuery to count the number of child elements (in this case list elements) inside div id #foo and then divide 100 / (# of counted child elements). The last step would be to apply that as a percentage based width

<style="width: Npx">

Where N = [100/(# of child elements)]?

Answer 1

Try this(it takes care of case when there are not children in foo):

var el = $('#foo');
var len = el.children().length;
if(len > 0){
    len = 100/len;
    el.css("width",  len + "px"); 
}