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