Execute multiple connect middlewares simultaneously

simultaneously.coffee

# Allows to execute multiple connect middlewares simultaneously. This is useful when you have middlewares
# that run asynchronously and should run in parallel rather than in a sequence.

# The function below takes a list of middlewares (as separate arguments), and returns a new middleware that
# executes all the passed middlewares together when invoked, and calls `next()` when all of them finish.


simultaneously = (middlewares...) -> (req, res, next)->
  left = middlewares.length
  one = (err) -> return next err if err?; --left or do next
  middleware req, res, one for middleware in middlewares
  return

# (written in CoffeeScript, compiled JavaScript below)

# Example usage:

app = connect()
app.use simultaneously middleware1, middleware2

simultaneously.js

var simultaneously,
  __slice = [].slice;

simultaneously = function() {
  var middlewares;
  middlewares = 1 <= arguments.length ? __slice.call(arguments, 0) : [];
  return function(req, res, next) {
    var left, middleware, one, _i, _len;
    left = middlewares.length;
    one = function(err) {
      if (err != null) {
        return next(err);
      }
      return --left || next();
    };
    for (_i = 0, _len = middlewares.length; _i < _len; _i++) {
      middleware = middlewares[_i];
      middleware(req, res, one);
    }
  };
};