What is procrastinate.js?

Ever wanted to do things later and one only thing at a time? Well now you can! You can even not do the thing if you are already doing one thing.

Usage

Basic usage

var p = new procrastinate({
	'events': {
		'beforeSave': 1, // No async
		'save': 2, // A little async
		'afterSave': 100 // Very async
	}
});

var log = [];

p.on('beforeSave', function() { log.push('Preparing to save') });
p.on('beforeSave', function() {
	var d = deferred();
	setTimeout(function() {
		// Wait a little before we start...
		log.push('Done waiting');
		d.resolve();
	}, 1000);
	return d.promise;
});
var save = function() {
	var d = deferred();
	setTimeout(function() {
		log.push('Save half-way');
		setTimeout(function() {
			log.push('Save completed');
			d.resolve();
		}, 1000);
	}, 1000);
	return d.promise;
};
p.on('save', save);
p.on('save', save);
p.on('save', save);
p.on('afterSave', function() {  log.push('Done saving, phew') });

// Call it
p.doNow();

log should contain:

Preparing to save
Done waiting
Save half-way
Save half-way
Save completed
Save completed
Save half-way
Save completed
Done saving, phew

Use case: autosave form to server without spamming the server

var p = new procrastinate(/* your events */);
p.on(/* your listeners */);

$('input, select, textarea').on('change', function() {
	p.doLater(3000); // Only do after 3 sec of inactivity
	// If 3 sec delay happens to expire when it is already saving it will be ignored
	// since enqueue is not set to true
});
$('.saveButton').on('click', function() {
	p.doNow(true); // Do now, enqueue if necessary.
    // Enqueue means that if something is running it will do after current task is done
});

Install

node

npm install --save procrastinate-queue

(The name "procrastinate" was actually taken...)

browser

<script src="build/browser/procrastinate.min.js"></script>

Methods

new procrastinate(customOptions)

Initialize with options that declare your event flow/order and max concurrency for each event.

Example:

var p = new procrastinate({
	'events': {
    	'validate': 1, 'beforeSave': 1, 'save': 2, 'afterSave': 10
    }
});

The events will be executed in the specified order. For example, beforeSave will run after all validate events have finished. Additionally, the listeneres to both validate and beforeSave will run sequentially. save will allow 2 listners to run simultaneously while afterSave will allow 10.

on(listener)

Add event listeners to your events. The listeners will be executed in the order they are added.

Both regular functions and deferred functions are supported.

Example:

p.on('save', function() {  /* Do something syncronously */ });
p.on('save', function() {  
	var d = deferred(); // Use: https://www.npmjs.com/package/deferred
    setTimeout(function() {
    	d.resolve();
    }, 1000);
    return d.promise();
});

doNow(enqueue = false)

Execute the event chain now. This method returns a promise which will be resolved once the entire event chain has completed.

If enqueue is false or undefined, and if there is already another event chain ongoing, this will do nothing, and the returned promise will resolve immediately.

Set enqueue to true to execute the event chain once the ongoing event chain has completed.

doLater(timeout, enqueue = false)

Execute the event chain when the timeout has expired. However, if doLater is called before the previous timeout has expired, it will cancel the previous doLater. This method returns a promise that resolves when the deferred event chain completes. (It will not resolve if it cleared. This behaviour might change in a future version.)

Set enqueue to true to execute the doLater after any ongoing event chain has completed.

A doNow clears any unenqueued doLater. To prevent your doLater from being cleared by a doNow set enqueue to true.

isDoing()

Returns true if an event chain is currently executing.

getDoing()

Get the promise for the ongoing event chain. If there is no ongoing event chain this will return an immediately resolved promise.

abort()

Calling this method while an event chain is ongoing will prevent the next event in the chain from executing. It will not abort the ongoing event because events might be running in parallell.