Parse.Object.previous() workaround for Parse.Cloud.beforeSave()

post.js

Parse.Cloud.beforeSave('Post', function (request, respond) {
  var post = request.object;
  var prevCatId = post.get('prevCat').id;
  var catId = post.get('cat').id;
  
  if (post.dirty('cat')) {
    var prev = new Parse.Query('Category');
    prev.get(prevCatId, {
      success: function (category) {
        // Decrement old category post count.
        category.increment('postCount', -1);
        category.save();
  
        // Update previous category manually in
        // a separate field. Boo!
        var prevCat = new Category();
        prevCat.id = prevCatId;
        post.set('prevCat', prevCat);
  
        // Increment new category post count.
        var next = new Parse.Query('Category');
        next.get(catId, {
          success: function (category) {
            category.increment('postCount');
            category.save();
            response.success();
          }
        });
      }
    });
  }
});