node-async-flow

An aggressive async flow solution for node.js.

The support for Generator is required.

Why?

node.js is excellent for it's advanced support for new standards. But it's been a headache as there are callbacks everywhere and it's hard to compose logic between them.

Peoples have been attempting to solve this situation for a long time:

The async provides handy utility functions to chain things together, along with a central error handing mechanism. It saves some nested callbacks but doesn't solve the problem.

There are also many Promise implementations, like q and bluebird. I personally dislike Promises because it's a standard which makes things harder: everything is in chainable callbacks and now we have a nice constructor and resolve and reject and then and catch, wow!

The co is the widely used generator-based solution for the callback hells. It's similar to the async/await standard and use Promises. To be used with co, everything should be Promises or "thunkified", which is another story.

Here comes the node-async-flow.

Features

• No wrapper needed for existing code (compared to new Promise and thunkify)
• No need to pass variables every next step
• Async in native loops
• In place error handling (if error is solvable let's continue)

Installation

npm install node-async-flow --save

Examples

See examples, tests, nwjs-download and nwjs-builder :)

Some code snippets:

const { exists, readFile } = require('fs'); const Flow = require('node-async-flow'); // Sleep 10 seconds. Flow(function*(cb) { console.log('now:', Date.now()); for(let i = 0; i < 10; i++) { yield setTimeout(cb.single, 1000); } console.log('now:', Date.now()); }); // Async check file exists and do something. Flow(function*(cb) { if(yield exists('package.json', cb.single)) { console.log('File exists.'); } }); // Async read file and parse JSON. Flow(function*(cb) { var [err, data] = yield readFile('package.json', { encoding: 'utf-8' }, cb.expect(2)); if(err) return console.error(err); var json = JSON.parse(data); // or, in single line. var [err, json] = yield readFile('package.json', { encoding: 'utf-8' }, (err, data) => err ? cb.expect(2)(err) : cb.expect(2)(null, JSON.parse(data)); if(err) return console.error(err); // or, use fs-extra. var [err, json] = yield require('fs-extra').readJson('package.json', cb.expect(2)); if(err) return console.error(err); }); // Destructuring. const getOneValue = (callback) => setTimeout(() => callback(true), 0); const getTwoValues = (callback) => setTimeout(() => callback(true, false), 0); const getThreeValues = (callback) => setTimeout(() => callback(true, false, null), 0); Flow(function*(cb) { var x = yield getOneValue(cb.single); // x == true. var x = yield getOneValue(cb.expect(1)); // x == [true]. var [x] = yield getOneValue(cb.expect(1)); // x == true. var [x, y] = yield getTwoValues(cb.expect(1)); // x == true, y == undefined. var [x, y] = yield getTwoValues(cb.expect(2)); // x == true, y == false. var {z, y, x} = yield getThreeValues(cb.map('x', 'y', 'z')); // x == true, y == false, z == null. });

License

MIT.