Update:
Now I would advise to have a look at:
-
The Promise object is used for deferred and asynchronous computations.
A Promise represents an operation that hasn’t completed yet, but is
expected in the future.A popular promises library is bluebird. A would advise to have a look at why promises.
You should use promises to turn this:
fs.readFile("file.json", function (err, val) { if (err) { console.error("unable to read file"); } else { try { val = JSON.parse(val); console.log(val.success); } catch (e) { console.error("invalid json in file"); } } });
Into this:
fs.readFileAsync("file.json").then(JSON.parse).then(function (val) { console.log(val.success); }) .catch(SyntaxError, function (e) { console.error("invalid json in file"); }) .catch(function (e) { console.error("unable to read file"); });
-
generators: For example via co.
Generator based control flow goodness for nodejs and the browser,
using promises, letting you write non-blocking code in a nice-ish way.var co = require('co'); co(function *(){ // yield any promise var result = yield Promise.resolve(true); }).catch(onerror); co(function *(){ // resolve multiple promises in parallel var a = Promise.resolve(1); var b = Promise.resolve(2); var c = Promise.resolve(3); var res = yield [a, b, c]; console.log(res); // => [1, 2, 3] }).catch(onerror); // errors can be try/catched co(function *(){ try { yield Promise.reject(new Error('boom')); } catch (err) { console.error(err.message); // "boom" } }).catch(onerror); function onerror(err) { // log any uncaught errors // co will not throw any errors you do not handle!!! // HANDLE ALL YOUR ERRORS!!! console.error(err.stack); }
If I understand correctly I think you should have a look at the very good async library. You should especially have a look at the series. Just a copy from the snippets from github page:
async.series([
function(callback){
// do some stuff ...
callback(null, 'one');
},
function(callback){
// do some more stuff ...
callback(null, 'two');
},
],
// optional callback
function(err, results){
// results is now equal to ['one', 'two']
});
// an example using an object instead of an array
async.series({
one: function(callback){
setTimeout(function(){
callback(null, 1);
}, 200);
},
two: function(callback){
setTimeout(function(){
callback(null, 2);
}, 100);
},
},
function(err, results) {
// results is now equals to: {one: 1, two: 2}
});
As a plus this library can also run in the browser.