jason-cooke / queuer.js

Run queue of tasks in JavaScript easily

queuer.js

Run easily queue of tasks.

Installation

It is available with bower or npm:

bower install queuer.js
npm install queuer.js

Include queuer.min.js to the HTML, and the queuer object is now available in the global scope:

<script type="text/javascript" src="/path/to/bower_components/queuer.js/dist/queuer.min.js"></script>

Alternately, you can use a module manager to avoid global scoping:

var queuer = require('queuer.js');
// or es6 import
import queuer from 'queuer.js';

Usage

Create a queue

var queue = queuer();

Register tasks on it

queue.task('task1', function(payload, queue) {
    // the payload will be either the result of the previous task
    // or the initial payload given to the queue if it is the first task
     
    // the queue argument is the task's queue
    
    console.log('I am a task');

    // if you want to deal with async task you must return a promise.
});

Running the queue

queue(initialPayload) // You can pass an initial payload to the queue
    .then(function(payload) {
        // everything worked
        // the payload is the result returned by the last task
    })
    .catch(function(error) {
        // an error occured, the queue was stopped
    });

Dealing with events

The queue is an event emitter. That means you can emit or listen events on it. The queue already emits some events:

• EVENT_TASK_START: A task was started.
• EVENT_TASK_STOP: A task was stopped.
• EVENT_TASK_ERROR: A task threw an error.
• EVENT_CANCEL: The queue was canceled.

To register an event listener use on(event, listener) or once(event, listener) method on the queue:

queue.on(queue.EVENT_TASK_START, function(taskName, payload) {
    // taskName was started with the given payload
    // other task events have the save listener signature
});

queue.once(queue.EVENT_CANCEL, function() {
    // the queue was cancelled
    // we use once instead of on because it will happen only once
});

As the queue is given as an argument to the task, you can use it in tasks to listen or to emit some custom event as you wish:

queue.task('task1', function(payload, queue) {
    queue.once(queue.EVENT_CANCEL, function() {
        // the queue was canceled, we use this to cancel our task's asynchronous operations
    });

    queue.on('myCustomEvent', function(data) {
        // we listen to our custom event
    });
});

queue.emit('myCustomEvent', 'test');

Cancel the queue

The queue exposes a shorcut method to cancel it queue.cancel(). You can pass arguments to it if you wish, they will be forwarded across the cancel event.

Development

Installation

make install

Build

make build or make build-dev (unminified version)

Watch

make watch

Test

make test

Contributing

All contributions are welcome and must pass the tests. If you add a new feature, please write tests for it.

License

This application is available under the MIT License.