Here is how I done the tag cloud of my blog. It is done mostly in jQuery. All my site is static and pages are generated with nanoc. It is (in my humble opinion) the modern geek way to make a website. The tagcloud should work for machine with and without javascript.

This is why I’ll give only a Ruby Generator, not a full javascript generator. But you can easily translate from Ruby to Javascript.

Here is what you should obtain:

jQuery

Here is the simple jQuery code:

    $(document).ready( function(){$('.list').hide();} );
    function tagSelected(id) {
        $('.list').hide();
        $('#'+id).fadeIn();
        $('.tag.selected').removeClass('selected');
        $('#tag_'+id).addClass('selected');
    }

This code will hide all the div containing links to articles containing the tag. And create a function do show the div containing the tag.

For each tag I create a span element:

    <span   style="font-size: 1.0em;"
            class="tag"
            onClick="tagSelected('[TAG]')"
            id="tag_[TAG]">
        [TAG]
    </span>

and a div containing links associtated to this tag:

    <div id="[TAG]">
        <h4>[TAG]</h4>
        <ul>
            <li> LINK 1 </li>
            <li> LINK 2 </li>
        </ul>
    </div>

nanoc

Here is how I generate this using nanoc 2.

If you want to make it fully jQuery one, it shouldn’t be too difficult, to use my ruby code and translate it into javascript.

In a first time tags correpond of the list of all tags.

def tags
    return @items.tags.join(', ')
end

A function to create a data structure associating to each tag its occurence.

# generate an hash tag => number of occurence of tag
def tagNumber
    tags={}
    @items.each do |p|
        if p.tags.nil?
            next
        end
        p.tags.each do |t|
            if tags[t]
                tags[t]+=1
            else
                tags[t]=1
            end
        end
    end
    return tags
end

I also need a data structure who associate to each tag a list of pages (at least url and title).

# generate an hash tag => [ page1, page2 ... ]
def tagRefs
    tagLinks={}
    @items.each do |p|
        if p.tags.nil?
            next
        end
        p.tags.each do |t|
            if tagLinks[t].nil?
                tagLinks[t]=[ p ]
            else
                tagLinks[t] <<= p
            end
        end
    end
    return tagLinks
end

Calculate the real size of each tag to be displayed.

I choosen not to use the full range of size for all the tag. Because if no tag has more than n (here 10) occurences, then it doesn’t deserve to be of the maximal size.

def tagRealSize
    tags=tagNumber
    max=tags.values.max
    min=tags.values.min
    # size in CSS em.
    minSize=1.0
    maxSize=2.5
    tagSize={}
    tags.each do |t,n|
        if ( max == min )
            tagSize[t]=minSize
        else
            # normalized value between 0 and 1
            # if not tag appear more than 10 times,
            # then it cannot have the maximal size
            tagSize[t]=[ ( n - min + 0.0 ) / ( max - min ) ,
                         (n - min) / 10.0 ].min
            # from normalized size to real size
            tagSize[t]=( tagSize[t] ) * (maxSize - minSize) + minSize
        end
    end
    return tagSize
end

Finaly a function to generate the XHTML/jQuery code

# generate an XHTML/jQuery code for tag cloud
def tagCloud
    tagLinks=tagRefs
    tagSize=tagRealSize

    # begin to write the code
    tagCloud=%{<script type="text/javascript">
        $(document).ready( function(){$('.list').hide();} );
        function tagSelected(id) {
            $('.list').hide();
            $('#'+id).fadeIn();
            $('.tag.selected').removeClass('selected');
            $('#tag_'+id).addClass('selected');
        }
    </script><div id="tagcloud">}
    # Creation of the tags <span>
    tagSize.sort{|a,b| a[0].downcase <=> b[0].downcase}.each do |t,s|
        tag_in_id=t.gsub(/\W/,'_')
        # HTML protected version of the tag
        # for example, replace ' ' by '&nbsp;'
        protected=t.gsub(/&/,'&amp;').gsub(/ /,'&nbsp;').gsub(/</,'&lt;').gsub(/>/,'&gt;')
        tagCloud <<= %{
            <span style="font-size: #{s}em;"
                  class="tag"
                  onClick="tagSelected('#{tag_in_id}')"
                  id="tag_#{tag_in_id}">
                #{protected}
            </span> }
    end
    tagCloud <<= %{</div><div id="hiddenDivs" >}
    # Creation of the divs containing links associated to a tag.
    tagLinks.each do |t,l|
        tag_in_id=t.gsub(/\W/,'_')
        tagCloud <<= %{
            <div id="#{tag_in_id}" class="list">
                <h4>#{t}</h4><ul>}
        # generate the link list
        l.each do |p|
            tagCloud <<= %{<li><a href="#{p.path}">#{p.title}</a></li>}
        end
        tagCloud <<= %{</ul></div>}
    end
    tagCloud <<= %{</div>}
    return tagCloud # yeah I know it is not necessary
end

You can download the complete file to put in your ‘lib’ directory.

Of course to be nice you need the associated CSS

// Change the color when mouse over
.tag:hover {
  color: #cc0000; }

// Change the color when tag selected
.tag.selected {
  color: #6c0000; }

// a bit of space and pointer cursor
.tag {
  cursor: pointer;
  margin-left: .5em;
  margin-right: .5em; }

That’s all folks.