Get-flow NPM | npm.io

get-flow

Node.js Flow Control Utility, powerful and easy to use

Installation

$ git clone --branch=master git://github.com/enricostara/get-flow.git
$ cd get-flow
$ npm install

Coding

Function runSeries(taskList, callback, ...) runs an Array of tasks - and yes, you can mix synchronous and asynchronous tasks! - in series, calling back when done or immediately if an exception occurs.

Each task must be a sync or async Function and all the async tasks must have the first argument named callback in order to be recognised as asynchronous.
Synchronous task will be internally executed surrounded by a try/catch statement, any exception stops the flow and it will be passed to the main callback as first argument.
ASynchronous task must manage any exception internally and propagate it to the callback as first argument
The arguments callback and tasks are mandatory (callback can be null but in place anyway), the subsequent arguments (if any) will be passed only to the first task .

See the following example where sync, async, sync tasks are executed in series:

var flow = require('get-flow');

function multiply(x, y) {
    return x * y;
}

function addMillis(callback, x) {  // for ASYNC task the first argument must be the callback and be named 'callback'
    var start = new Date().getTime();
    setTimeout(function () {
        var millis = new Date().getTime() - start;
        callback(null, x + millis);
    }, 100);
}

function sqrt(x) {
    return Math.sqrt(x);
}

flow.runSeries(
    [   // tasks series
        multiply, // sync
        addMillis, // async
        sqrt  // sync again
    ],
    function(ex, result) {    // a proper callback when the last task (sqrt) is done
        console.log('no exception, (ex == null) = %s ', ex == null);
        console.log('result = %s', result);
        var assert = require('assert');
        assert.equal(result >= 10, true);
    },
    2, 3 // x and y passed at first task (multiply)
);

Function retryUntilIsDone(callback, retriesLimit, task, ...) calls the given async task until succeeds or the retries limit has been reached (the default is 10 attempts)

All the arguments are mandatory (callback and retriesLimit can be null but in place anyway), the subsequent arguments (if any) will be passed to the task.

See the following example

var flow = require('get-flow');

var i = 0;

function task(callback, input) {
    setTimeout(function () {
        i++;
        if (i === 5) {
            callback(null, input + i);
        } else {
            callback('err')
        }
    }, 10);
}

flow.retryUntilIsDone(
    function (ex, result) { // a proper callback
        console.log('no exception, (ex == null) = %s ', ex == null);
        console.log('result = %s', result);
        var assert = require('assert');
        assert.equal(result, 15);
    },
    null, // retries limit will be the default = 10
    task, // the async task
    10  // argument for the task
);