Bag.js Save

JS / CSS / files loader + key/value storage

Project README

bag.js - JS / CSS loader + KV storage

Build Status NPM version

bag.js is loader for .js / .css and other files, that uses IndexedDB/ WebSQL / localStorage for caching. Consider it as alternative for other types of loaders for modern browsers, that reduce number of server requests, especially for mobile devices. Also bag.js can be used as simple key/value storage, that doesn't require you to know details about IndexedDB and WebSQL.

This project is inspired by basket.js, but provides more safe storages for big assets and universal key/value interface. Key features are:

  • Parallel load and sequential execution for JS / CSS and other types of files
  • Use IndexedDB / WebSQL / localStorage - no size limits for big assets.
  • KV storage for objects, with simple interface.
  • You can use multiple instances with different storage options. For example Indexeddb + WebSQL for assets and localStorage for user settings.
  • Partial compatibility with basket.js.


This package requires Promise polyfill for old browsers. We recommend lie, it's small enougth and fast.


via bower:

bower install bag.js

via npm:

bower install bagjs --save



var bag = new window.Bag();

bag.require(['/site.css', '/jquery.js', '/site.js'])
  .then(() => {
    // code to run after loading
    // ...
  .catch(err => console.log('loading error: ', err));


var bag = new window.Bag({
  prefix: 'my_namespace',
  stores: ['indexeddb', 'websql'],
  timeout: 20000,
  expire: 24

bag.isValidItem = function(source, obj) {
  return (source && (source.url === obj.url)) ? true : false;

var files = [
  { url: '/site.css', expire: 1 },
  { url: '/jquery.js', expire: 10 },
  { url: '/site.js' },
  { url: '/more_styles.css', expire: 5, execute: false }

  .then(data => {
    console.log('loaded', data);
  .catch(err => console.log(err));

You can skip new keyword. Also, you can use callbacks:

window.Bag().require([ '/site.css', '/site.js']
  .then(data => {
  .catch(err => console.log(err));

Using as key/value storage:

var obj = { lorem: 'ipsum' };
var bag = new window.Bag();

bag.set('dolorem', obj)
  .then(() => bag.get('dolorem'));
  .then(data => console.log('Loaded data:\n', data));
  .catch(err => console.log(err));
  .then(() => bag.remove('dolorem'));


Note, all methods with optional callbacks will return promises if callback is not set.

new Bag([options])

Object constructor. You can also define options after constructor call, via instance properties (they have the same names). Options (hash):

  • prefix - Data namespace. Default - bag. Used to separate data for multiple instances.
  • stores - Array of storage names to use, ordered by preference. Default ['indexeddb', 'websql', 'localstorage'].
  • timeout - files loading timeout, in seconds. Default 20.
  • expire - require() data expiration, in hours. Default - 1 month. 0 or unset - don't expire.

Note 1: you can skip new keyword, calling Bag() will return you new instance anyway.

Note 2: prefix must be set before require/get/set/remove/clear calls. Other options can be changed anytime.

.require(files) -> Promise

  1. Load files from server or from cache.
  2. Inject known types into page (js/css by default), unless execution is disabled. When multiple files requested (files are Array), those are loaded in parallel, but injected in defined order.
  3. Also, content of the files is returned in the result.

files param can be:

  • Object - resource info (see details below).
  • String - just resource url, other params will be default.
  • Array(Object|String) - list of resources to load in parallel.

resource info:

  • url - resource URI, required.
  • expire - optional, expiration time in hours. 0 or not set - don't expire.
  • key - the name, used to store loaded file, if not defined, then url will be used.
  • unique - a token stored with the cached item. If you request the same item again with a different token the script will be fetched and cached again.
  • live - force cache bypass, for development needs.
  • cached - force request from cache only.

result (Promise):

  • (Array|String) with loaded content, depending on files type. If a single resource is requested (Object|String), data is String. If an Array of resources is requested, or chained call done, data is array of strings.

Note, unless you pass resources info in short form, input objects are extended with loaded data.

.get(key) -> Promise

Load data by key name. Not existing values are returned as undefined.

.set(key, data [, expire]) -> Promise

Put data into storage under key name.

  • key - String to address data.
  • data - JS object to store. We currently support only objects, serializable by JSON. Don't try to put functions or arraybuffers.
  • expire - Expiration time in seconds. Don't expire by default.

.remove(key) -> Promise

Remove key data from store.

.clear([expiredOnly]) -> Promise

Clear all storage data (in your namespace), or just expired objects when called as bag.clear(true).

.addHandler(types, handler)

Add handler for loaded files with specified mime types. By default, handlers for application/javascript and text/css already exist. If you set execute: false in resource info, then handler will not be applied.

  • types - String with mime type or Array of strings.
  • handler - function to "execute" file of that type.


Remove handler for specified mime type (opposite to addHandler).



Open Source Agenda is not affiliated with "Bag.js" Project. README Source: nodeca/bag.js
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