stewardess

serial async flow control

npm install stewardess
5 downloads in the last week
50 downloads in the last month

Stewardess

She keeps track of your serial async methods.

Also provies a small bag of peanuts and half a can of soda.

Install

npm install stewardess

Usage:

var stewardess = require('stewardess')

function first(next) {
  console.log('first');
  next();
}

function second(next) {
  console.log('second');
  next();
}

function third(next) {
  console.log('third');
  next();
}

stewardess(
  first,
  second,
  third
).run();

stewardess has lot's of chainable methods:

stewardess(
  function(next) {
    // this function goes second
    next();
  }
)
.add(function(next) {
  // this function goes third
  next();
})
.addBefore(function(next) {
  // this function goes first
  next();
}),
.before(function() {
  // this is called before each function
})
.after(function() {
  // this is after before each function
})
.done(function() {
  // this is called when all methods finish
})
.error(function(err) {
  // if any method throws an error,
  // or calls next(err), it ends up here
})
.final(function() {
  // this is called after done or error is called
})
.context({'some':'object'}) // set this-ness for all callbacks
.run(); // this starts it

you can also pass arguments into run(), which will be sent to each method along the way

stewardess(
  function(meow, mix, next) {
    meow === 'meow';
    mix.meow === 'mix';
    mix.meow = mix.meow.toUpperCase();
    next();
  },
  function(meow, mix, next) {
    meow === 'meow';
    mix.meow === 'MIX';
    next();
  }
)
.after(function(meow, mix) {
  // before, after, and done also get arguments
})
.error(function(err, meow, mix) {
  // error gets arguments with the error
})
.run('meow', {meow: 'mix'});

you can reuse a stewardess instance by calling bind()

Here is an example of using stewardess to provide middleware for an http server. It gives the length of each piece of middleware and for the entire request.

"use strict";

var http = require('http')
  , stewardess = require('./index')

var handle = stewardess(
  function(req, res, next) {
    req.startTime = process.hrtime();
    next();
  },
  function(req, res, next) {
    console.log(req.url + ' requested');
    next();
  },
  function(req, res, next) {
    if (req.headers && /^curl/.test(req.headers['user-agent'])) {
      res.end('yur usin curl!');
      next('break'); // fire 'done' and stop
    } else {
      next();
    }
  },
  function(req, res, next) {
    res.end('oh hai');
    next();
  }
)
.before(function(req, res) {
  req.i = req.i + 1 || 1;
  req.lastStart = process.hrtime();
})
.after(function(req, res) {
  var t = process.hrtime(req.lastStart);
  console.log('middleware ' + req.i + ' took %d seconds and %d ms', t[0], t[1]/1000000);
})
.done(function(req, res) {
  var t = process.hrtime(req.startTime);
  console.log(req.url + ' served in %d seconds and %d ms', t[0], t[1]/1000000);
})
.done(function(req, res) {
  console.log(req.url + ' served with status ' + res.statusCode);
  console.log();
})
.bind();

http.Server(handle).listen(8080);

Call next('skip') to skip a method

stewardess(
  function(options, next) {
    options.meow = 'mix';
    next('skip');
  },
  function(options, next) {
    throw new Error('should never run');
  }, 
  function(options, next) {
    console.log(options.meow);
  }
)
.run({});

Call next('repeat') to repeat a step

stewardess(function(next) {
    // this will repeat infinitely
    next('repeat');
}).run();

Call next('break') to skip to the end

stewardess(
  function(options, next) {
    options.meow = 'mix';
    next('break');
  },
  function(options, next) {
    throw new Error("should never run");
  }
)
.done(function(options) {
  assert.equal(options.meow, 'mix');
})
.run({});

Call next('previous') to go back one method

This allows for a pattern of checking and filling a cache.

var cache = null;

var checkCache = stewardess(
  function checkCache(next) {
    if (cache) {
      return next('skip');
    }
    next();
  },

  function setCache(next) {
    cache = 8;
    next('previous');
  },

  function useCache(next) {
    assert.equal(cache, 8);
    next();
  }
)
.bind();

Create plugins to repeat setup

function myRillyCoolPlugin(stewardess, pluginOptions) {
  if (pluginOptions.rilly === 'ossum') {
    console.log('yur ossum');
  }

  stewardess
  .before(function(options, name) {
    console.log('entering ' + name);
  })
  .after(function(options, name) {
    console.log('leaving ' + name);
  })
  .done(function(options) {
    console.log('all done!');
  });
}

var pluginOptions = {
  rilly: 'ossum'
}

stewardess(
  function first(options, next) {
    options.foo = 'bar';
  },
  function second(options, next) {
    options.baz = 'bam';
  },
  function third(options, next) {
    options.fish = 'sticks';
  }
)
.plugin(myRillyCoolPlugin, pluginOptions)
.run({});

Stewardess comes with a couple of handy plugins

All of the builtin stewardess plugins require the first argument to be an object.

stewardess(
  function first(options, next) {
    setTimeout(next, 100);
  },
  function second(options, next) {
    for (var i = 0; i < 10000; ++i) {
      Math.pow(i);
    }
    next();
  }
)
.plugin(stewardess.plugins.timer) // print the milliseconds taken for each method
.plugin(stewardess.plugins.hrTimer) // same as timer, but with nanosecond precision
.plugin(stewardess.plugins.overallTime) // print the time for the entire stack to run
.run({});

Mongoose Queries

Stewardess will recognize mongoose queries, and run them for you. You just need to make sure the first parameter is an object, and call comment to tell stewardess which property to store the results under.

stewardess(

  MongoosePersonModel
    .find()
    .select({ name: 1, age: 1 })
    .sort('age')
    .comment('people'), // this tells stewardess where to put the results

  function printPeople(options, next) {
    options.people.forEach(function(person) {
      console.log(person.name, person.age);
    });
    next();
  }

)
.run({});

Testing

Run npm test. Requires mocha.

License

stewardess is published under an MIT style license.

npm loves you