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

• Create a stepper
• Register listeners for any events you're interested in
• Add some functions using stepper's add() method
• 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