queue-promise

queue-promise

A simple and small library for promise-based queues.

Installation

$ npm install queue-promise

This module uses several ECMAScript 2015 (ES6) features. You'll need the latest Node.js version in order to make it work correctly. You might need to run the script with the --harmony flag, for example:

$ node --harmony index.js

Usage

"use strict";

const Queue = require( "./src/index.js" );
const debug = ( msg, err ) => {
    return () => new Promise( ( resolve, reject ) => {
        if ( err ) reject( `Error: ${msg}` );
        resolve( `Success: ${msg}` );
    } );
};

const q = new Queue( {
    concurrency : 1,
    interval    : 2000
} );

q.on( "resolve", ...data => console.log( data ) );
q.on( "reject", error => console.error( error ) );

q.add( debug( "Index 0" ) );
q.add( debug( "Index 1", true ) );
q.add( debug( "Index 2", true ) );
q.add( debug( "Index 3" ) );

q.start();

Generated output:

[ 'Success: Index 0' ]  < after 2s
Error: Index 1          < after 4s
Error: Index 2          < after 6s
[ 'Success: Index 3' ]  < after 8s

API

new Queue( options )

Create a new Queue instance with optionally injected options.

Option	Default	Description
concurrency	10	How many promises can be handled at the same time
interval	250	How often should new promises be handled (in ms)

public .add( promise )

Adds a promise to the queue.

public .start()

Starts the queue.

public .stop()

Stops the queue.

private .next()

Goes to the next request and stops the loop if there is no requests left.

public .on( event, callback )

Sets a callback for an event. You can set callback for those events:

• start
• stop
• tick
• resolve[ ...output ]
• reject[ message ]
• end

Tests

$ npm test