A polyfill for IndexedDB using WebSql
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README.md

IndexedDB Polyfill

Build Status Dependencies devDependencies npm Bower CDNJS License

Live Demo!

Use a single, indexable, offline storage API across all desktop and mobile browsers and Node.js.

Even if a browser natively supports IndexedDB, you may still want to use this shim. Some native IndexedDB implementations are very buggy. Others are missing certain features. There are also many minor inconsistencies between different browser implementations of IndexedDB, such as how errors are handled, how transaction timing works, how records are sorted, how cursors behave, etc. Using this shim will ensure consistent behavior across all browsers.

Features

Installation

You can download the development or production (minified) script, or install it using NPM or Bower.

Please note that the version currently in master is the only one which supports Node.js (and has a number of fixes), but we are not yet ready for release.

Bower

bower install IndexedDBShim

npm

npm install indexeddbshim

Browser set-up

Add the following script to your page:

<script src="dist/indexeddbshim.min.js"></script>

If you need full Unicode compliance (handling special non-alphanumeric identifiers in store and index names), use the following instead:

<script src="dist/indexeddbshim-UnicodeIdentifiers.min.js"></script>

Node set-up

const setGlobalVars = require('indexeddbshim');
global.window = global; // We'll allow ourselves to use `window.indexedDB` or `indexedDB` as a global
setGlobalVars(); // See signature below

Usage/API

For the browser scripts, if the browser already natively supports IndexedDB and is not known to be buggy, then the script won't do anything.

Otherwise, assuming WebSQL is available, the script will add the IndexedDB API to the browser (unless you use one of the non-invasive files, in which case setGlobalVars can be used to optionally add the API to an object of your choosing; if you also wish Unicode support, you will need to add it yourself).

Either way, you can use IndexedDB just like normal. Here's an example.

setGlobalVars(<winObj or null>, initialConfig)

In the non-invasive builds (and Node.js), globals are not automatically set. You have the choice to set globals when you wish as well as to set the API on an object of your choosing in place of setting globals.

This is done through setGlobalVars() (which is otherwise called in the browser builds automatically with no arguments).

This function defines shimIndexedDB, indexedDB, IDBFactory, etc. on one of the following objects in order of precedence:

  1. The passed in winObj object if defined
  2. window (for Node, define global.window = global;)
  3. self (for web workers)
  4. A new object

The initialConfig argument, if present, should be an object whose keys are the config properties to set and its values are the config values (see shimIndexedDB.__setConfig below).

If you are adding your own window.openDatabase implementation, supplying it within initialConfig (keyed as openDatabase) will ensure that shimIndexedDB.__useShim() is auto-invoked for you if poor IndexedDB support is detected.

shimIndexedDB.__useShim();

To force IndexedDBShim to shim the browser's native IndexedDB (if our code is not already auto-shimming your browser when detecting poor browser support), add this method call to your script.

On browsers that support WebSQL, this line will completely replace the native IndexedDB implementation with the IndexedDBShim-to-WebSQL implementation.

On browsers that don't support WebSQL, but do support IndexedDB, this line will patch many known problems and add missing features. For example, on Internet Explorer, this will add support for compound keys.

If CFG.addNonIDBGlobals has been set (e.g., on the initialConfig argument of setGlobalVars), the other non-IndexedDB shims necessitated by this library will be polyfilled as possible on the chosen "global" (i.e., ShimEvent, ShimCustomEvent, ShimEventTarget, ShimDOMException, and ShimDOMStringList). Mostly useful for testing.

If CFG.fullIDLSupport has been set, the slow-performing Object.setPrototypeOf calls required for full WebIDL compliance will be used. Probably only needed for testing or environments where full introspection on class relationships is required. See this SO topic

shimIndexedDB.__forceClose(connIdx, msg)

The spec anticipates the closing of a database connection with a forced flag.

The spec also mentions some circumstances where this may occur:

A connection may be closed by a user agent in exceptional circumstances, for example due to loss of access to the file system, a permission change, or clearing of the origin’s storage.

Since the latter examples are under the browser's control, this method may be more useful on the server or for unit-testing.

If the first argument, connIdx is missing (or null or undefined), all connections will be force-closed. It can alternatively be an integer representing a 0-based index to indicate a specific connection to close.

The second argument msg will be appended to the AbortError that will be triggered on the transactions of the connection.

Individual IDBDatabase database connections can also be force-closed with a particular message:

db.__forceClose(msg);

shimIndexedDB.__debug(boolean)

The IndexedDB polyfill has sourcemaps enabled, so the polyfill can be debugged even if the minified file is included.

To print out detailed debug messages, add this line to your script:

shimIndexedDB.__debug(true);

shimIndexedDB.__setConfig()

Rather than using globals, a method has been provided to share state across IndexedDBShim modules.

Configuration can be set early in the non-invasive browser and Node builds via the second argument to setGlobalVars() (see its definition above).

Its signature (for setting configuration after shimIndexedDB is created) is:

shimIndexedDB.__setConfig({property: value, property2: value2, ...});

or:

shimIndexedDB.__setConfig(property, value);

Configuration options

The available properties relevant to browser or Node are:

  • DEBUG - Boolean (equivalent to calling shimIndexedDB.__debug(val))
  • cursorPreloadPackSize - Number indicating how many records to preload for caching of (non-multiEntry) IDBCursor.continue calls. Defaults to 100.
  • UnicodeIDStart and UnicodeIDContinue - Invocation of createObjectStore and createIndex calls for validation of key paths. The specification technically allows all IdentifierName](https://tc39.github.io/ecma262/#prod-IdentifierName) strings, but as this requires a very large regular expression, it is replaced by default with [$A-Z_a-z] and [$0-9A-Z_a-z], respectively. Note that these are and must be expressed as strings, not RegExp objects. You can use this configuration to change the default to match the spec or as you see fit. In the future we may allow the spec behavior via optional dynamic loading of an internal module.
  • win, Object on which there may be an openDatabase method (if any) for WebSQL; Defaults to window or self in the browser and for Node, it is set by default to node-websql.
  • DEFAULT_DB_SIZE - Used as estimated size argument (in bytes) to underlying WebSQL openDatabase calls. Defaults to 4 * 1024 * 1024 or 25 * 1024 * 1024 in Safari (apparently necessary due to Safari creating larger files and possibly also due to Safari not completing the storage of all records even after permission is given). Has no effect in Node (using node-websql), and its use in WebSQL-compliant browsers is implementation dependent (the browser may use this information to suggest the use of this quota to the user rather than prompting the user regularly for say incremental 5MB permissions).

The following config are mostly relevant to Node but has bearing on the browser, particularly if one changes the defaults.

  • addNonIDBGlobals - If set to true will polyfill the "global" with non-IndexedDB shims created by and sometimes returned publicly by the library. These include ShimEvent, ShimCustomEvent, ShimEventTarget, ShimDOMException, and ShimDOMStringList. Mostly useful for debugging (and in Node where these are not available by default).
  • fullIDLSupport - If set to true, the slow-performing Object.setPrototypeOf calls required for full WebIDL compliance will be used. Probably only needed for testing or environments where full introspection on class relationships is required. See this SO topic
  • escapeDatabaseName - Due to the Node implementation's reliance on node-websql/node-sqlite3 which create files for each database (and the fact that we haven't provided an option to map filename-safe IDs to arbitrary, user-supplied IndexedDB database names), when the user creates IndexedDB databases, the Node implementation will be subject to the limitations systems can have with filenames. Since IndexedDBShim aims to facilitate code that can work on both the server and client, we have applied some escaping and restrictions by default. The default behavior is to prefix the database name with D_ (to avoid filesystem, SQLite, and node-sqlite3 problems if the user supplies the IndexedDB-permitted empty string database name), to escape ^ which we use as our own generally-filename-supported escape character, to escape NUL (which is also problematic in SQLite identifiers and in node-sqlite3 in general) as ^0, to escape upper-case letters A-Z as ^A, ^B, etc. (since IndexedDB insists on case-sensitivity while file systems often do not), to escape any characters mentioned in databaseCharacterEscapeList (as ^1 + a two-hexadecimal-digit-padded sequence), and to throw an Error if databaseNameLengthLimit is not set to false and is surpassed by the resulting escaped name. You can use this escapeDatabaseName callback property to override the default behavior, with the callback accepting a single argument of the user's database name choice and returning your own filename-safe value. Note that we do escape NUL and our own escape character (^) before passing in the value (for the above-mentioned reasons), though you could unescape and return your own escaped format. While some file systems may not have the other restrictions, you should at a minimum anticipate the possibility for empty strings (since we rely on the result of this function for internal escaping as a SQLite identifier) as well as realize the string ":memory:" will, if unescaped, have a special meaning with node-sqlite3. You can make the escaping more lax, e.g., if your file system is case-sensitive, or you could make it more stringent (e.g., escaping other case-sensitive Unicode characters--a PR would incidentally be welcome, as well as one to optionally support node-sqlite3's interpretation of the empty string and ":memory:" types for creating temporary databases).
  • unescapeDatabaseName - Not used internally; usable as a convenience method for unescaping strings formatted per our default escaping conventions
  • databaseCharacterEscapeList - When this property and escapeDatabaseName are not overridden, the following characters will be escaped by default, even though IndexedDB has no such restrictions, as they are restricted in a number of file systems, even modern, Unicode-supporting ones: 0x00-0x1F 0x7F " * / : < > ? \ |. This property can be overridden with a string that will be converted into an alternate regular expression or supplied with false to disable any character limitations.
  • databaseNameLengthLimit - When this property and escapeDatabaseName are not overridden, an error will be thrown if the escaped filename exceeds the length of 254 characters (the shortest typical modern file length maximum). Provide a number to change the limit or supply false to disable any length checking.

The following config items are for Node only and are mostly for development debugging.

shimIndexedDB.__getConfig()

For retrieving a config value:

shimIndexedDB.__getConfig(property);

Known Issues

All code has bugs, and this project is no exception. If you find a bug, please let us know about it. Or better yet, send us a fix! Please make sure someone else hasn't already reported the same bug though.

Here is a summary of main known issues to resolve:

  1. blocked and versionchange IDBVersionChangeEvent event support
  2. Blob/File/FileList/ImageBitmap cloning through typeson-registry and test ImageData in Node through node-canvas

There are a few bugs that are outside of our power to fix. Namely:

Browser rollback

While we do try to rollback the database version in the browser when called for, we are not able to prolong WebSQL transactions so as to be able to benefit from the auto-rollback they perform upon encountering an error nor does WebSQL permit manual ROLLBACK commands so that we could undo the various WebSQL calls we need to make up IndexedDB transactions.

The special build of websql that we use does allow such IndexedDB-spec-compliant (and data-integrity-friendly!) rollback behavior.

iOS

Due to a bug in WebKit, the window.indexedDB property is read-only and cannot be overridden by IndexedDBShim. There are two possible workarounds for this:

  1. Use window.shimIndexedDB instead of window.indexedDB
  2. Create an indexedDB variable in your closure

By creating a variable named indexedDB, all the code within that closure will use the variable instead of the window.indexedDB property. For example:

(function() {
    // This works on all browsers, and only uses IndexedDBShim as a final fallback
    var indexedDB = window.indexedDB || window.mozIndexedDB || window.webkitIndexedDB || window.msIndexedDB || window.shimIndexedDB;

    // This code will use the native IndexedDB, if it exists, or the shim otherwise
    indexedDB.open("MyDatabase", 1);
})();

Windows Phone

IndexedDBShim works on Windows Phone via a Cordova/PhoneGap plug-in. There are two plugins available: cordova-plugin-indexedDB and cordova-plugin-indexeddb-async. Both plug-ins rely on a WebSQL-to-SQLite adapter, but there are differences in their implementations. Try them both and see which one works best for your app.

Building

To build the project locally on your computer:

  1. Clone this repo If you clone the repository to work against an unstable version, you only need to clone the repository recursively (via git clone https://github.com/axemclion/IndexedDBShim.git --recursive) if you wish to have the W3C tests available for testing (which unfortunately loads all W3C tests into the "web-platform-tests" subdirectory rather than just the IndexedDB ones). Otherwise, just use git clone https://github.com/axemclion/IndexedDBShim.git

  2. Install dev dependencies (and websql for Node) npm install

  3. Run the build script npm start

  4. Done

The output files will be generated in the dist directory

Testing

There are currently three folders for tests, tests-qunit, tests-mocha and tests-polyfill (the latter are also Mocha-based tests, but at present its W3C tests only work in Node).

They can be run through a variety of means as described below.

To properly build the files (lint, browserify, and minify), use npm start or to also keep a web server, run npm run dev (or grunt dev). If you wish to do testing which only rebuilds the browser files, run npm run dev-browser and if only testing Node, run npm run dev-node. But before release, one should run npm run build (or npm run dev).

The tests produce various database files. These are avoided in .gitignore and should be cleaned up if the tests pass, but if you wish to delete them all manually, run npm run clean.

Browser testing

All QUnit-based tests should pass in modern browsers.

All Mocha-based browser tests should pass except for one test having a problem in Firefox.

Automated browser unit testing

Follow all of the steps above to build the project, then run npm test or npm run sauce-qunit (or npm run phantom-qunit or grunt phantom-qunit to avoid using Saucelabs when you have credentials set up as environmental variables) to run the unit tests.

Note that when not running Saucelabs, the tests are run in PhantomJS, which is a headless WebKit browser.

The older PhantomJS version has problems with two tests, however: index.openCursor(range) and IDBObjectStore.openKeyCursor due apparently to a bug with the WebKit browser used in the older PhantomJS implementation (but the tests themselves report as having such problems).

Manual browser testing

If you want to run the tests in a normal web browser, you'll need to spin-up a local web server and then open tests-qunit/index.html?noglobals and/or tests-mocha/index.html in your browser. You can also run npm run dev and point your browser to http://localhost:9999/tests-qunit/index.html or http://localhost:9999/tests-mocha/index.html.

Note that, for the Mocha tests, you probably wish to "Switch to IndexedDBShim" when doing the testing since otherwise, it will only test the native implementation.

Node Testing

To run the Node tests, run the following:

  1. npm run node-qunit - The full test suite sometimes does not complete execution.
  2. npm run mocha
  3. npm run tests-polyfill (or its components npm run fake, npm run mock, npm run w3c-old). Note that only fake is currently passing in full, however.
  4. npm run w3c (you must first run git submodule update --init --recursive (possibly without init too if using an older version of Git), git submodule foreach --recursive git fetch, and git submodule foreach git merge origin master or git submodule foreach git pull --ff-only origin master). Note that some of these tests may not be passing because of the test environment not being completely configured for Node. We are working on fixing this. There are some older and less complete W3C tests that can be run with npm run w3c-old, but the goal is to remove these once the new ones are configured properly and working in the browser as do the old tests.

To run a specific Mocha test (which includes the tests-polyfill tests), run npm --test=... run mocha.

Testing in a Cordova/PhoneGap app

If you want to run the tests in a Cordova or PhoneGap app, then you'll need to create a new Cordova/PhoneGap project, and add the IndexedDB plug-in. Then copy the contents of our tests directory into your project's www directory. Delete our index.html file and rename cordova.html to index.html.

Contributing

Pull requests or Bug reports welcome!