jQuery determine if ul has class OR another one

You could use is instead?

if ($('#menu-item-49').is('.current-menu-item, .current-menu-parent')) {
  $('ul.sub-menu ').css('display', 'block');
}

Check the current matched set of
elements against a selector and return
true if at least one of these elements
matches the selector.

Beats having to use multiple hasClass queries, which is the alternative:

if ($('#menu-item-49').hasClass('current-menu-item') || 
    $('#menu-item-49').hasClass('current-menu-parent')) {
  $('ul.sub-menu ').css('display', 'block');
}