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spl.js

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SpatiaLite for browser & node

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# spl.js

SpatiaLite 5.1.1-rc0 and friends - sqlite 3.51.1, geos 3.14.1, proj 9.7.1, rttopo 1.1.0 - for node (sync API) and browser (async API).

[Here is a list](doc/spatialite_functions.md) of supported SpatiaLite SQL functions and [a list](doc/extensions_functions.md) of available SQLite extension functions/modules.

## Install

```bash
npm install spl.js
```

The library for browsers bundles both the WebWorker script and the wasm file (~4.5MB, ~3.4MB gzipped).

A minimal proj.db including EPSG codes for lon/lat to "Web Mercator" and UTM is embeded. Other PROJ files and the complete proj.db are available from the `dist/proj` folder.
If you like to use the full proj.db instead you need to mount it (e.g. `spl.fs.mount('proj', [...])`) and set the path with spatialite's `PROJ_SetDatabasePath('/proj/proj.db')`.

## Code Examples

Hello SpatiaLite

```js
import SPL from 'spl.js';
const db = await SPL().then(spl => spl.db());

console.assert(
    await db.exec('SELECT spatialite_version()').get.first === '5.1.1-rc0'
);

db.exec('SELECT ? AS hello', ['spatialite']).get.objs
    .then(results => console.assert(results[0].hello === 'spatialite'))
    .catch(err => console.log(err));
```

Import a GeoPackage

```js
import SPL from 'spl.js';

const spl = await SPL();
const url = 'https://data.london.gov.uk/download/london_boroughs/9502cdec-5df0-46e3-8aa1-2b5c5233a31f/london_boroughs.gpkg'

const london = await fetch(url)
    .then(response => response.arrayBuffer());

const db = await spl.db(london)
    .exec('SELECT EnableGpkgAmphibiousMode()');

const srid = await db.exec('SELECT SRID(geom) FROM london_boroughs').get.first;

console.assert(srid === 27700)
```

Handle JSON & GeoJSON automatically (parse, stringify, geometry blob to GeoJSON)

```js
import SPL from 'spl.js';
const db = await SPL({
    autoGeoJSON: {
        precision: 0,
        options: 0
    }
}).then(spl => spl.db());

console.assert(
    (await db.exec('SELECT json(@js)', { '@js': { hello: 'json' }}).get.first).hello === 'json'
);

console.assert(
    (await db.exec('SELECT GeomFromText(?)', [ 'POINT(11.1 11.1)' ]).get.first).coordinates[0] === 11
);
```

Import a zipped Shapefile

```js
import SPL from 'spl.js';
const spl = await SPL();

const lights = await fetch('examples/lights.zip')
    .then(response => response.blob());

const db = await spl
    .fs.mount('data', [
        { name: 'lights.zip', data: lights }
    ])
    .db()
        .exec('SELECT ImportZipSHP(?, ?, ?, ?, ?)', [
            '/data/lights.zip', 'lights', 'lights', 'UTF-8', 4326
        ]);

console.assert(
    await db.exec('SELECT count(*) FROM lights').get.first === 17976
);
```

## Live Examples

Be patient - spl.js, data and other packages need to be fetched.

**Note**: These GitHub Pages examples only work in Chrome/Safari due to a [known Firefox bug](https://github.com/bdon/ghpages-firefox-range-bug) where range requests return compressed file sizes.

Create a topology from a GeoPackage layer and simplify polygon boundaries:

https://jvail.github.io/spl.js/examples/topology.html

Load proj.db remotely, transform and display GeoPackage geometries in OpenLayers:

https://jvail.github.io/spl.js/examples/openlayers.html

Buffers & Intersections: A little test for GeoJSON vs WKB serialization and WebWorker transfer:

https://jvail.github.io/spl.js/examples/lights-performance.html

Sources: https://github.com/jvail/spl.js/tree/main/examples

A few notebook / observablehq [examples](https://observablehq.com/search?query=%22spl.js%22&sort=relevance&direction=desc&useES=true).

## API

The API for node and browser is identical (almost - file handling is obviously different. See the `fs` namespace).

If you are looking for more examples there are many snippets in the `test/node.js` and `test/browser.js` files.

## SPL

### `SPL`([`options`: {}, `extensions`: []]) -> `Promise<SPL>`

extensions: Browser only - see "Extensions API" section below.

options:
- `autoJSON`: If 'true' applies stringify/parse to/from JSON in results and query parameters automatically (default: true)
- `autoGeoJSON`: Automatically converts SpatiaLite/GPKG geometry blobs into GeoJSON if not set to 'false' (default { precision: 6, options: 0 }):
    - `precision`: precision used in Geometry to GeoJSON conversion,
    - `options`: options as described in "AsGeoJSON" in SpatiaLite:
        - 0 no options
        - 1 GeoJSON BoundingBox
        - 2 GeoJSON CRS [short version]
        - 3 BoundingBox + short CRS
        - 4 GeoJSON CRS [long version]
        - 5 BoundingBox + long CRS

### `.db`([`path`: string | ArrayBuffer]) -> `DB`

### `.version`() -> `VersionInfo`

Returns an object with version strings for all bundled libraries: `spatialite`, `sqlite`, `geos`, `proj`, `rttopo`, `spl`.

### `.terminate`()

Terminates the WebWorker (only Browser).

## FS (Filesystem)

All filesystem operations are under the `fs` namespace.

**Browser**

### `.fs.mount`(`path`: string, options) -> `SPL`

options is an array of objects:

{ `name`: string, `data`: ArrayBuffer | Blob | File | FileList | string };

If a db is opened from a mounted path it is read only. Use db.load('path/name') to load it as read/write db.
If `data` is a string it must be a valid URL where HEAD and Range requests are available. `name` is not required for File or FileList.

You can use SQLite URIs (https://sqlite.org/c3ref/open.html#urifilenameexamples). For mounted URLs you should use `file:sqlite.db?immutable=1`.

### `.fs.file`(`path`: string) -> ArrayBuffer

Read a file from the virtual filesystem. Returns the file contents as ArrayBuffer.

### `.fs.dir`(`path`: string) -> string[]

List directory contents. Returns an array of filenames.

### `.fs.unlink`(`path`: string) -> `SPL`

Delete a file from the virtual filesystem.

### `.fs.mkdir`(`path`: string) -> `SPL`

Create a directory in the virtual filesystem.

### `.fs.unmount`(`path`: string) -> `SPL`

Unmount a previously mounted path.

**Node**

### `.fs.mount`(`path`: string [, `mountpoint`: string]) -> `SPL`

If no mountpoint is provided the local `path` will be mounted as root e.g. `a_dir/some_dir/some_file` is available as `some_dir/some_file` if mounted as `spl.fs.mount('a_dir')`.

### `.fs.unmount`(`path`: string) -> `SPL`

## DB

### `.attach`(`db`: string, `schema`: string) -> `DB`
### `.detach`(`schema`: string) -> `DB`
### `.exec`(`sql`: string [, `parameters`: any]) -> `DB`

`parameters` is either an array (or array of arrays) with positional bindings or an object (or array of objects) with named bindings with the following (SQLite) templates:

- ?
- ?NNN
- :VVV
- @VVV
- $VVV

If `autoJSON` is enabled (by default) there is some ambiguity when `parameters` is an array.
Here I can not infer if you want to select 2 rows with values 1 and 2 or a JSON array of [1,2].

```js
db.exec('select json(?)', [1,2]);
```
In such cases it is better to use named parameters for JSON types.
```js
db.exec('select json($js)', { $js: [1,2] });
```

### `.read`(`sql`: string) -> `DB`

Read a SQL script with multiple statements.

### `.load`(`src`: string) -> `DB`

Import a database into the current database. This is using SQLite's backup API.

### `.save`([`dest`: string]) -> `DB` | ArrayBuffer

Export the current database. This is using SQLite's backup API.
If `dest` [**Node Only**] is undefined or empty an ArrayBuffer is returned.

### `.close`() -> `SPL`

### `.get`

A result object with the following properties (*thenables* in a browser):

### `.first` -> any
### `.flat` -> any[]
### `.rows` -> any[][]
### `.cols` -> string[]
### `.objs` -> {}[]
### `.sync` -> a synchronous result object

With `sync` (browser only) all ArrayBuffers will be transfered without copying (transferables) from the WebWorker.

### `.free`() -> void

Free result memory. Called automatically after accessing result properties, but can be called manually if needed.

## Extensions API (Browser only)

Sometimes you want to run code inside the WebWorker. With this API you can supply additional functions to extend the `SPL` and `DB` APIs executed inside the WebWorker.

Extension functions are available via the `ex` namespace: `db.ex.myFn()` and `spl.ex.myFn()`.

Example: https://jvail.github.io/spl.js/examples/extensions.html

### TypeScript Types

Two extension types are available:

- `DbExtension` - extends the database API, functions receive `DbSync` as first argument
- `SplExtension` - extends the SPL API, functions receive `SplSync` as first argument

```ts
import type { DbExtension, SplExtension } from 'spl.js';
```

### Example Code

```js
/** @type {import('spl.js').DbExtension} */
const dbExtension = {
    extends: 'db',
    fns: {
        tables: db => db.exec('SELECT name FROM sqlite_master WHERE type=\'table\''),
        master: (db, type) => db.exec('SELECT name FROM sqlite_master WHERE type=?', [type])
    }
};

/** @type {import('spl.js').SplExtension} */
const splExtension = {
    extends: 'spl',
    fns: {
        spatialite_version: spl => {
            const db = spl.db();
            const version = db.exec('SELECT spatialite_version()').get.first;
            db.close();
            return version;
        }
    }
};

const spl = await SPL({}, [dbExtension, splExtension]);
const db = await spl.db()
    .read(`
        CREATE TABLE hello (world);
        CREATE VIEW hello_view AS SELECT * FROM hello;
    `);

console.assert(await db.ex.tables().get.first === 'hello');
console.assert(await db.ex.master('view').get.first === 'hello_view');
console.assert(await spl.ex.spatialite_version() === '5.1.1-rc0');
```

## Building and Testing

Requirements:
- An activated emsdk environment (4.0.x) - https://emscripten.org/docs/tools_reference/emsdk.html
- Fossil SCM for fetching SpatiaLite sources - https://fossil-scm.org/

All C dependencies are fetched from the web. The sqlean git submodule needs to be initialized before running the build script.

```bash
git submodule update --init
npm install && npm run build:all
```

Running Node & Browser tests

```bash
npm run test:node && npm run test:firefox && npm run test:chrome
```

Running (the relevant) SpatiaLite test cases - this will take quite some time ... ~ 45 minutes or more.
Requires node >= v21 to run test cases without .mjs extension.

```bash
npm run test:libspatialite
```

## Performance

I did not create any fancy benchmark scripts. This is just a rough figure obtained from running a few tests with rttopo:

- In node the performance is ~ 75% of the native SpatiaLite
- In the browser perfomance is ~ 50% (including some overhead from the WebWorker communication)

## License

This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program.  If not, see <http://www.gnu.org/licenses/>.

spl.js

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