source: trunk/www.guidonia.net/wp/wp-content/plugins/simple-tags/2.7/inc/js/helper-add-tags.js@ 44

function addTag(tag) {
        // Trim tag
        tag = tag.replace( /^\s+/, '' ).replace( /\s+$/, '' );

        if ( document.getElementById("adv-tags-input") ) { // Tags input from Simple Tags
        
                var tag_entry = document.getElementById("adv-tags-input");
                if ( tag_entry.value.length > 0 && !tag_entry.value.match(/,\s*$/) ) {
                        tag_entry.value += ", ";
                }
                
                var re = new RegExp(tag + ",");
                if ( !tag_entry.value.match(re) ) {
                        tag_entry.value += tag + ", ";
                }
                
        } else { // Default tags input from WordPress
                
                var newtags = jQuery('#tags-input').val();
                newtags += ',' + tag;

                // massage
                newtags = newtags.replace( /\s+,+\s*/g, ',' ).replace( /,+/g, ',' ).replace( /,+\s+,+/g, ',' ).replace( /,+\s*$/g, '' ).replace( /^\s*,+/g, '' );
                jQuery('#tags-input').val( newtags );
                tag_update_quickclicks();
                
        }
}