Automatically Discover Document Links And Apply Class. This will look through every a element on the page. If the href attribute of it has a .doc, .xls, or .pdf in it, it will apply the appropriate class name to it (e.g. class="doc").

/**
 * This will look through every a element on the page. If the href attribute
 * of it has a .doc, .xls, or .pdf in it, it will apply the appropriate class
 * name to it (e.g. class="doc")
 */
$('a[href]').each(function () {
  if ((C = $(this).attr('href').match(/[.](doc|xls|pdf)$/))) {
    $(this).addClass(C[1]);
  }
});