wrap-angular-promise-usage.js

_.merge = wrapFunct(_.merge);
_.union = wrapFunct(_.union);

_.merge(AJAX.get('foo'), [ 'en' ], AJAX.get('bar'));

wrap-angular-promise.js

// $q comes from angular

function wrapFunct(fn) {
  return function() {
    var context = this;
    var args = [].slice.call(arguments);
    var resolved = $q.all(args.map($q.when));

    return resolved.then(function(values) {
      return fn.apply(context, values);
    });
  };
}