@expo/websql

NOTE: This is Expo's fork without the 'sqlite3' dependency which is unused in React Native.

node-websql  
====

The [WebSQL Database API][websql], implemented for Node
using sqlite3. In the browser, it falls back to window.openDatabase.

Install
----

npm install websql

Usage
----

``js
var openDatabase = require('websql');
`

Create a SQLite3 database called mydb.db:

`js
var db = openDatabase('mydb.db', '1.0', 'description', 1);
`

Create an in-memory database:

`js
var db = openDatabase(':memory:', '1.0', 'description', 1);
`

API
---

$3

The name is the name of the database. It's passed verbatim to [sqlite3][].

The version is the database version (_currently ignored - see below_).

The description and size attributes are ignored, but they are required for
compatibility with the WebSQL API.

The callback just returns the same database object returned
synchronously (_migrations currently aren't supported - see below_).

For more information how to use the WebSQL API, see [the spec][websql] or
various tutorials.

For more information on sqlite3, see the SQLite3 readme.

$3

You can also use this module in the browser (via Browserify/Webpack/etc.),
in which case it will just use
window.openDatabase, meaning you are subject to browser WebSQL support.

$3

Both readTransaction() (read-only) and transaction() (read-write) are supported.
readTransaction() has some small performance optimizations, so it's worthwhile to
use if you're not writing any data in a transaction.

Goals
----

The [WebSQL Database API][websql] is a deprecated
standard, but in many cases it's useful to reuse legacy code
designed for browsers that support WebSQL. Also, it allows you to quickly
test WebSQL-based code in Node, which can be convenient.

The goal of this API is to exactly match the existing WebSQL API, as implemented
in browsers. If there's any difference between browsers (e.g. rows[0] is supported
in Chrome, whereas only rows.item(0) is supported in Safari), then the lowest-common
denominator version is exported by this library.

This library has a robust test suite, and has been known to pass the PouchDB
test suite as well.

Non-Goals
---

This library is _not_ designed to:

- Invent new APIs, e.g. deleting databases, supporting BLOBs, encryption, etc.
- Support WebSQL in Firefox, IE, or other non-WebSQL browsers

In other words, the goal is not to carry the torch of WebSQL,
but rather to bridge the gap from existing WebSQL-based code to Node.js.

Custom SQLite3 bindings
----

This library is designed to allow swappable SQLite3 implementations, beyond
just node-sqlite3. Examples:

* node-websql itself
* Cordova SQLite Plugin 2
* React Native SQLite 2

To create your own custom implementation, use this API:

`js
var customOpenDatabase = require('websql/custom');
var openDatabase = customOpenDatabase(SQLiteDatabase);
`

This SQLiteDatabase implementation needs to be a constructor-style function
with a constructor signature like so:

`js
// takes a single argument: the database name
var db = new SQLiteDatabase('dbname');
`

Then it implements a single function, exec(), like so:

`js
function exec(queries, readOnly, callback) {
// queries: an array of SQL statements and queries, with a key "sql" and "args"
// readOnly: whether or not these queries are in "read only" mode
// callback: callback to be called with results (first arg is error, second arg is results)
}
`

Here is the full specification:

$3

Construct a new SQLiteDatbase object, with the given string name.

$3

Execute the list of SQLQuerys. If we are in readOnly mode, then any
non-SELECT queries need to throw an error without executing. This function calls the Node-style
callback with an error as the first argument or the Array as
the second argument.

$3

A SQL query and bindings to execute. This can be a plain JavaScript object or a custom class,
as long as it has the following members:

#### sql (String)

The SQL query to execute.

#### args (Array)

The arguments to bind the query.

E.g.:

`js
{
sql: 'INSERT INTO foo values (?, ?)',
args: ['bar', 'baz']
}
`

$3

A result returned by a SQL query. This can be a plain JavaScript object or a custom class,
as long as it has the following members:

#### error

A JavaScript Error object, or undefined if the SQLQuery did not throw an error. If error is truthy, then it's assumed insertId, rowsAffected, and rows are falsy (they will be ignored anyway).

#### insertId (number)

An insertion ID representing the new row number, or undefined if nothing was inserted.

#### rowsAffected (number)

The number of rows affected by the query, or 0 if none.

#### rows (Array<object>)

The rows returned by a SELECT query, or empty if none.

Each object is a mapping of keys (columns) to values (value fetched).

E.g.:

`js
{
insertId: undefined,
rowsAffected: 0,
rows: [
{'foo': 'bar'},
{'foo': 'baz'},
]
}
`

Or:

`js
{
error: new Error('whoopsie')
}
`

For an example implementation (and the one used by this module)
see lib/sqlite/SQLiteDatabase.js.

TODOs
---

The versioning and migration APIs
(i.e. changeVersion())
are not supported. Pull requests welcome!

Limitations
----

1. With the restrictions of the node-sqlite3 API
on database names ("Valid values are filenames, ":memory:" for an anonymous
in-memory database and an empty string for an anonymous disk-based
database") and our lack of interest to enforce a particular mapping that
honors the WebSQL spec
in its indicating that "All strings including the empty string are valid database
names" (and that they are case-sensitive), consumers will need to do their
own mapping for strings in order to 1) avoid problems with invalid filenames or
filenames on case insensitive file systems, and to 2) avoid user databases being
given special treatment if the empty string or the string ":memory:" is used;
another special purpose form of string supported by SQLite that may call for
escaping are file::memory:...
URLs.

2. Although neither the WebSQL spec nor SQLite speaks to this matter,
node-sqlite3 has the following additional
limitations
which are surfaced for our users: namely, that statements will only be
executed up to the first NULL byte and SQL comments
will lead to runtime errors.

Testing
----

First:

npm install

Main test suite:

npm test

Linter:

npm run lint

Test in debug mode (e.g. with the node-inspector`):

npm run test-debug

Run the test suite against actual WebSQL in a browser:

npm run test-local

Run the actual-WebSQL test against PhantomJS:

npm run test-phantom

[websql]: https://www.w3.org/TR/webdatabase/
[sqlite3]: https://github.com/mapbox/node-sqlite3