bubble errors back up your big ol' nested callback chain
JavaScript
Latest commit 522488c Dec 13, 2014 @brianc Merge pull request #4 from MorganLindqvist/master
Fixed typos in README.md
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README.md Fixed typos in README.md Dec 13, 2014
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README.md

okay

Bubble errors back up your big ol' nested callback chain.

If domains are in use, defer the error to the domain's error handler by using process.domain.intercept transparently.

without okay

function doSomething(path, cb) {
  fs.readDir(path, function(err, files) {
    if(err) return cb(err);
    async.map(files, fs.readFile, function(err, contents) {
      if(err) return cb(err);
      return cb(null, contents.join('\n'));
    });
  });
};

with okay

var ok = require('okay');

function doSomething(path, cb) {
  fs.readDir(path, ok(cb, function(files){
    async.map(files, fs.readFile, ok(cb, function(contents) {
      return cb(null, contents.join('\n'));
    }));
  });
};

The same code with annotations:

var ok = require('okay');

function doSomething(path, cb) {

  //if path does not exist, bubble the error out to the
  //callback function right away
  //if there was no error, call the new error-less cb

  fs.readDir(path, ok(cb, function(files){

    //if there was an error reading any file, bubble the error out to the
    //callback function right away
    //if there was no error, call the new error-less cb

    async.map(files, fs.readFile, ok(cb, function(contents) {
      return cb(null, contents.join('\n'));
    }));
  });
};

okay also supports a single callback:

function doSomethingOrDie(path, callback) {

  //if there is an error with fs.readDir, THROW it
  //if there was no error, call the new error-less callback

  fs.readDir(path, ok(function(files) {

    //if there was an error reading any file, THROW it
    //if there was no error, call the new error-less callback

    async.map(files, fs.ReadFile, ok(function(contents) {
      return callback(null, contents.join('\n'));
    }));
  });
};

or even no callback at all:

//if there is an error with fs.writeFile, THROW it
//if there was no error, do nothing

fs.writeFile('/some/file', 'hello', ok());

domains

Throwing errors is probably not what you want to do.

Okay comes in really handy if you are using domains. It transparently passes the error back into the active domain if it exists, or it calls your callback with the error parameter already removed in the happy circumstance where there is no error. It's basically shorthand for process.domain.intercept but will fall back to throwing exceptions if domains are not activated or you're currently not bound to a domain.

var ok = require('okay');
var domain = require('domain');
var count = 0;
var handler = function(req, res) {
  var requestDomain = domain.create();
  req.id = new Date() + (count++);
  requestDomain.add(req);
  requestDomain.add(res);
  requestDomain.on('error', function(err) {
    console.log('error handling request ' + req.id);
    console.log(err);
    try {
      res.end(500);
    } catch(e) {
      console.log('could not send response 500 code');
    }
  });
  process.nextTick(function() {
    setTimeout(function() {
      //read some missing file to cause an error
      //the error will fire on the request's domain
      //and WILL NOT crash the server
      if(count % 2) {
        fs.readFile('omsdflksjdflsk', ok(function(contents) {
          res.writeHead(200);
          res.end('ok');
        }));
      } else {
        //this exception will fire on the request's domain
        //as well and will also NOT crash the server
        process.nextTick(ok(function() {
          throw new Error("I Broke it.")
        }));
      }
    }, 1000);
  })
}

var serverDomain = domain.create();
serverDomain.on('error', function(e) {
  console.log('something happened with the server!')
  console.log(e);
});
serverDomain.run(function() {
  var http = require('http');
  var server = http.createServer(handler);
  server.listen(80);
});

express + okay

var ok = require('okay');
get('/', function(req, res, next) {
  fs.readFile('file.txt', 'utf8', ok(next, function(contents) {
    res.send(contents);
  });
});

coffee-script + express + okay

ok = require "okay"
app.get "/", (req, res, next) ->
  fs.readFile "file.txt", "utf8", ok next, (contents) ->
    res.send(contents)

mocha + okay

var ok = require('okay');
describe('a directory', function() {
  it('exists', function(done) {
    fs.readdir(__dirname, ok(done, function(files){
      assert.equal(1, files.length);
      done();
    }));
  });
});

code golf, baby.

license

MIT