middleware-flow

Middleware control flow library

Installation

npm install middleware-flow

Examples

series(middlewares...)

var series = require('middleware-flow').series;
var app = require('express')();

app.use(series(mw1, mw2, mw2)); // equivalent to app.use(mw1, mw2, mw3);

parallel(middlewares...)

var parallel = require('middleware-flow').parallel;
var app = require('express')();
                                  // runs the middlewares in 'parallel'
app.use(parallel(mw1, mw2, mw2)); // if err, returns the first error that occurred

parallelWait(middlewares...)

var parallelWait = require('middleware-flow').parallelWait;
var app = require('express')();
                                  // runs the middlewares in 'parallel' and waits for all of them before to return also in case of err
app.use(parallelWait(mw1, mw2, mw2)); // if err, returns the first error that occurred

each

var each = require('middleware-flow').each;
var arr = [1,2,3];
var app = require('express')();
                                  // runs the middlewares in 'parallel'
app.use(
  each(arr,
    // runs the middlewares in parallel
    function (eachReq, res, next) {
      // eachReq is a scoped req for the each function that reads from req,
      // but writes to it's own scope (prototypically inherits from request)
    },
    function (item, req, eachReq, res, next) {
      // if middleware accepts five arguments, the current item and the original req are passed
      // eachReq is a scoped req for the each function that reads from req,
      // but writes to it's own scope (prototypically inherits from request)
    })
); // if err, returns the first error that occurred

or(middlewares...)

var or = require('middleware-flow').or;
var app = require('express')();
                                             // runs the middlewares in series, until one passes (no next(err));
app.use(or(user.isOwner, user.isModerator)); // if err, returns the first error that occurred

and(middlewares...)

Same as series.

if(value).then(middlewares...).else(middlewares...)

var if = require('middleware-flow').if;
var app = require('express')();

app.use(
  if(true)
    .then(one, two, three)
    .else(error)
);

syncIf(fn).then(middlewares...).else(middlewares...)

var syncIf = require('middleware-flow').syncIf;
var app = require('express')();

app.use(
  syncIf(nameQueryExists)   // accepts a sync function that returns a boolean
    .then(one, two, three)  // true -> then, error -> skips all next(err)
    .else(error)
);
function nameQueryExists (req, res) {
  return exists(req.query.name);
}
function exists (val) {
  return val !== null && val !== undefined;
}

asyncIf(fn).then(middlewares...).else(middlewares...)

var asyncIf = require('middleware-flow').asyncIf;
var or = require('middleware-flow').or;
var fs = require('fs');
var app = require('express')();

app.use(
  asyncIf(bodyFileExists)    // expects boolean as the result argument
    .then(one, two, three)   // true -> then, false -> else, error -> skips all next(err)
    .else(other)
);
function logExists (req, res, cb) {
  fs.exists(req.body.file, function (exists) {
    cb(null, exists);
  });
}

mwIf(middleware).then(middlewares..).else(middlewares..)

var mwIf = require('middleware-flow').mwIf;
var app = require('express')();

app.use(
  mwIf(userIsModerator)    // error here, just runs the else middlewares
    .then(one, two, three) // no error -> then, error -> else
    .else(other)           // if other is an error middleware it will recieve
                           //   the error else the error will be ignored
);
function userIsModerator (req, res, next) {
  if (!req.user.isModerator) {
    next(new Error('access denied'));
  }
  else {
    next();
  }
}

try(middlewares..).catch(middlewares..)

var flow = require('middleware-flow');
var app = require('express')();

app.use(
  flow.try(saveUser) // error here, just runs the catch middlewares
    .catch(rollback) // no error -> other, error -> rollback
                     // if rollback is an error middleware it will recieve
                     //   the error else the error will be ignored
);
function saveUser (req, res, next) {
  db.save(req.user, next);
}

bg(middlewares...)

app.use(
  flow.bg(mw1, mw2, mw2)
); // runs the middlewares in series in the background

License

MIT