/*
 * Validate track selection: any tracks selected?
 */
function submitTrackSelection() {
  var pids = document.getElementsByClassName( 'product_id' );
  if( pids ) {
    for( var i = 0; i < pids.length; i++ ) {
      if( pids[i].checked ) {
        var f = $( 'trackselectionform' );
        f.submit();
        return;
      }
    }
  }
  alert( 'Please select tracks to buy!' );
}

/*
 * Validate order: email?
 */
function orderValidateEmail() {
  var email = $( 'emailfield' ).value;
  if( !email ) {
    alert( "Please enter a valid email address." );
    return;
  }
  var emailReg = "^[\\w-_\.]*[\\w-_\.]\@[\\w]\.+[\\w]+[\\w]$";
  var regex = new RegExp( emailReg );

  if( regex.test( email )) {
    var f = $('orderform');
    f.submit();
  }
  else {
    alert( "Please enter a valid email address." );
    return;
  }
}