javascript - Node.js: What techniques are there for writing clean, simple callback code?

Question

node.js code is known for turning into callback spaghetti.

What are the best techniques for overcoming this problem and writing clean, uncomplex, easy to understand callback code in node.js?

Answer 1

Take a look at Promises: http://promises-aplus.github.io/promises-spec/

It is an open standard which intended to solve this issue.

I am using node module 'q', which implements this standard: https://github.com/kriskowal/q

Simple use case:

var Q = require('q');

For example we have method like:

var foo = function(id) {
  var qdef = Q.defer();

  Model.find(id).success(function(result) {
    qdef.resolve(result);
  });

  return (qdef.promise);
}

Then we can chain promises by method .then():

foo(<any-id>)
.then(function(result) {
  // another promise
})
.then(function() {
  // so on
});

It is also possible to creating promise from values like:

Q([]).then(function(val) { val.push('foo') });

And much more, see docs.

See also:

• http://jeditoolkit.com/2012/04/26/code-logic-not-mechanics.html#post
• http://wiki.commonjs.org/wiki/Promises/A