Routes for a user controller in a Node.js application
Looking at users.js, you can see that I tried to DRY things up by creating sequelizeSuccessHandler and sequelizeErrorHandler (I hate those names), but there's still a lot of repetition. 


I suppose you're talking about these repeated lines in the route handlers:


  .then(sequelizeSuccessHandler(response))
  .catch(sequelizeErrorHandler(response));



I don't really know Node,
but it seems to me that you could add another helper function:

function handle(query, response) {
  query
  .then(sequelizeSuccessHandler(response))
  .catch(sequelizeErrorHandler(response));
});

router.get('/', function(request, response) {
  handle(User.findAll(), response);
});

router.post('/', function(request, response) {
  handle(User.create(User.params(request.body)), response);
});


(The names "handle", and "query" might not be the best.)