An aggressive async flow solution for node.js.
npm install node-async-flowAn aggressive async flow solution for node.js.
The support for Generator is required.
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.
* 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)
``bash`
npm install node-async-flow --save
See examples, tests, nwjs-download and nwjs-builder :)
Some code snippets:
`javascript
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.
});
``
MIT.