stepper

stepper

Stepper and Grouper classes for running an arbitrary number of tasks in series or parallel

Motivation

Eliminate some boilerplate when using step.

Usage

1. Create a stepper
2. Register listeners for any events you're interested in
3. Add some functions using stepper's add() method
4. Call stepper's walk() method

Examples

Running some sync and async tasks one after another

var Stepper = require('../lib/stepper').Stepper;

var stepper = new Stepper();

// add steps
stepper.add(function(err, val) {
    console.log('running step 1 (sync)');
    return 1;
});
stepper.add(function(err, val) {
    if (err) throw err;
    console.log('running step 2 (sync)');
    return 2;
});
stepper.add(function(err, val) {
    if (err) throw err;
    console.log('running step 3 (async)');
    var self = this;
    console.log('wait 2 seconds...');
    setTimeout(function() {
        console.log('completed step 3 (async)');
        self();
    }, 2000);
});
stepper.add(function(err, val) {
    console.log('running step 4 (sync)');
    return 4;
});

// handle completion
var onComplete = function(err, val) {
    if (err) throw err;
    console.log('stepping is complete');
    console.log('return value: ' + val + '\n');    
};

// run steps
console.log('\nstart stepping...');
stepper.walk(onComplete);

Output

start stepping...
running step 1 (sync)
running step 2 (sync)
running step 3 (async)
wait 2 seconds...
completed step 3 (async)
running step 4 (sync)
stepping is complete
return value: 4

Run some async tasks in parallel

var Grouper = require('../lib/stepper').Grouper;

var grouper = new Grouper();

// setup group functions
grouper.add(function(fn) {
    console.log('running step 1 (async)');
    console.log('wait 3 seconds...');
    setTimeout(function() {
        console.log('completed step 1 (async)');
        fn(null, 1);
    }, (1000 * 3));
});
grouper.add(function(fn) {
    console.log('running step 2 (async)');
    console.log('wait 2 seconds...');
    setTimeout(function() {
        console.log('completed step 2 (async)');
        fn(null, 2);
    }, (1000 * 2));
});
grouper.add(function(fn) {
    console.log('running step 3 (async)');
    console.log('wait 1 second...');
    setTimeout(function() {
        console.log('completed step 3 (async)');
        fn(null, 3);
    }, (1000));
});

// handle completion
var onComplete = function(err, vals) {
    if (err) throw err;
    console.log('group is complete');
    console.log('return values: ' + vals + '\n');
};

// run steps
console.log('\nstart group...');
grouper.walk(onComplete);

Output

start group...
running step 1 (async)
wait 3 seconds...
running step 2 (async)
wait 2 seconds...
running step 3 (async)
wait 1 second...
completed step 3 (async)
completed step 2 (async)
completed step 1 (async)
group is complete
return values: 1,2,3

You can also add() Steppers and Groupers. See examples/nesting.js

Credits

Inspired by and dependent on step