I'm dynamically creating option elements for a drop down menu using Javascript and would like to know how to add a class to them so that I can style them with CSS.

I have the following code:

for (var i=0;i<portfolio.length-1;i++) {
    portfolioSelect.options[portfolioSelect.options.length] =
        new Option(portfolio[i]);
}

where portfolio is an array populated by an outside source.

HTML where options inserted:

<select id="portfolio" name="portfolio">
    <option selected="selected" value="Select One">Select One</option>
</select>