collection of callback hell and fixes from various websites

callBackHell.js

// http://thecodebarbarian.com/2015/03/20/callback-hell-is-a-myth
// some things changed because I have to copy from image
describe('.totalValue', function()
  it('should calculate the total value of items in a space', function(done){
    var table = new Item('table', 'dining room', '1', '3000');
    var chair = new Item('chair', 'living room', '3', '300');
    var couch = new Item('couch', 'living room', '2', '1100');
    var chair2 = new Item('chair', 'dining room', '4', '500');
    var bed = new Item('bed', 'bed room', '1','2000');
    
    table.save(function(){
      chair.save(function(){
        couch.save(function(){
          chair2.save(function(){
           bed.save(function(){
             Item.totalValue({room: 'dining room'}, function(totalValue){
               expect(totalValue).to.equal(5000);
               done();
             })
           }); 
          });
        });
      });
    });
  });
)};

// fix #1
function create(items, callback) {
  var numItems = items.length;
  var done = false;
  for (var i = 0; i < items.length; ++i) {
    items[i].save(function(error) {
      if (done) {
        return;
      }
      if (error) {
        done = true;
        return callback(error);
      }
      --numItems || callback();
    });
  }
}

// fix 2
function create(items, callback, index) {
  index = index || 0;
  if (index >= items.length) {
    callback();
  }
  items[i].save(function(error) {
    if (error) {
      return callback(error);
    }
    create(items, callback, index + 1);
  });
}