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node-websql

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The WebSQL Database API, implemented for Node.js

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node-websql
====

The [WebSQL Database API][websql], implemented for Node
using [sqlite3](https://github.com/mapbox/node-sqlite3). In the browser, it falls back to `window.openDatabase`.

_**Note:** [WebSQL is being deprecated by browsers](https://developer.chrome.com/blog/deprecating-web-sql/). This package
is most useful in Node.js and other environments where you want to emulate WebSQL._

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
---

### openDatabase(name, version, description, size [, callback])

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](http://www.html5rocks.com/en/tutorials/webdatabase/todo/) [tutorials](html5doctor.com/introducing-web-sql-databases/).

For more information on `sqlite3`, see [the SQLite3 readme](sqlite3).

### In the browser

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](http://caniuse.com/#feat=sql-storage).

### readTransaction() vs transaction()

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 `BLOB`s, 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](https://github.com/mapbox/node-sqlite3). Examples:

* [node-websql itself](https://github.com/nolanlawson/node-websql/blob/7c6327c2bbcf48bb0ac26f8f689206b7227baf81/lib/sqlite/SQLiteDatabase.js)
* [Cordova SQLite Plugin 2](https://github.com/nolanlawson/cordova-plugin-sqlite-2/blob/6bc32a4e71a3eea28fbc98c4da7e87c56156d094/src/javascript/SQLiteDatabase.js)
* [React Native SQLite 2](https://github.com/noradaiko/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:

### SQLiteDatabase(name (String))

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

### exec(queries (Array<SQLQuery>), readOnly (boolean), callback (function))

Execute the list of `SQLQuery`s. 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<SQLResult>` as
the second argument.

### SQLQuery

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<String>)

The arguments to bind the query.

E.g.:

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

### SQLResult

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&lt;object&gt;)

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()`](https://www.w3.org/TR/webdatabase/#dom-database-changeversion))
are not supported. Pull requests welcome!

Limitations
----

1. With the restrictions of the [node-sqlite3 API](https://github.com/mapbox/node-sqlite3/wiki/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](https://www.w3.org/TR/webdatabase/#dom-opendatabase)
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:...`](https://sqlite.org/inmemorydb.html)
[URLs](https://sqlite.org/uri.html#uri_format).

2. Although neither the WebSQL spec nor SQLite speaks to this matter,
`node-sqlite3` has the following additional
[limitations](https://github.com/mapbox/node-sqlite3/wiki/API#databaseexecsql-callback)
which are surfaced for our users: namely, that statements will only be
executed up to the first NULL byte and [SQL comments](https://sqlite.org/lang_comment.html)
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

node-websql

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