npm package: @linhttbk97/indexdb-worker-sqljs
Description: SQLite library with support for opening and writing databases, prepared statements, and more. This SQLite library is in pure javascript (compiled with emscripten).
Latest version: 1.0.6

<img src="https://user-images.githubusercontent.com/552629/76405509-87025300-6388-11ea-86c9-af882abb00bd.png" width="40" height="40" />

# SQLite compiled to JavaScript

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*sql.js* is a javascript SQL database. It allows you to create a relational database and query it entirely in the browser. You can try it in [this online demo](https://sql.js.org/examples/GUI/). It uses a [virtual database file stored in memory](https://emscripten.org/docs/porting/files/file_systems_overview.html), and thus **doesn't persist the changes** made to the database. However, it allows you to **import** any existing sqlite file, and to **export** the created database as a [JavaScript typed array](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Typed_arrays).

*sql.js* uses [emscripten](https://emscripten.org/docs/introducing_emscripten/about_emscripten.html) to compile [SQLite](http://sqlite.org/about.html) to webassembly (or to javascript code for compatibility with older browsers). It includes [contributed math and string extension functions](https://www.sqlite.org/contrib?orderby=date).

sql.js can be used like any traditional JavaScript library. If you are building a native application in JavaScript (using Electron for instance), or are working in node.js, you will likely prefer to use [a native binding of SQLite to JavaScript](https://www.npmjs.com/package/sqlite3). A native binding will not only be faster because it will run native code, but it will also be able to work on database files directly instead of having to load the entire database in memory, avoiding out of memory errors and further improving performances.

SQLite is public domain, sql.js is MIT licensed.

## API documentation
A [full API documentation](https://sql.js.org/documentation/) for all the available classes and methods is available.
Is is generated from comments inside the source code, and is thus always up to date.

## Usage

By default, *sql.js* uses [wasm](https://developer.mozilla.org/en-US/docs/WebAssembly), and thus needs to load a `.wasm` file in addition to the javascript library. You can find this file in `./node_modules/sql.js/dist/sql-wasm.wasm` after installing sql.js from npm, and instruct your bundler to add it to your static assets or load it from [a CDN](https://cdnjs.com/libraries/sql.js). Then use the [`locateFile`](https://emscripten.org/docs/api_reference/module.html#Module.locateFile) property of the configuration object passed to `initSqlJs` to indicate where the file is. If you use an asset builder such as webpack, you can automate this. See [this demo of how to integrate sql.js with webpack (and react)](https://github.com/sql-js/react-sqljs-demo).

```javascript
const initSqlJs = require('sql.js');
// or if you are in a browser:
// const initSqlJs = window.initSqlJs;

const SQL = await initSqlJs({
  // Required to load the wasm binary asynchronously. Of course, you can host it wherever you want
  // You can omit locateFile completely when running in node
  locateFile: file => `https://sql.js.org/dist/${file}`
});

// Create a database
const db = new SQL.Database();
// NOTE: You can also use new SQL.Database(data) where
// data is an Uint8Array representing an SQLite database file

// create a database from file
const filePath = `sql/data.sqlite`
const db  = new SQL.Database(filePath, (tableName)=>{
  //todo called when table changed
}, {filename: true})


// Execute a single SQL string that contains multiple statements
let sqlstr = "CREATE TABLE hello (a int, b char); \
INSERT INTO hello VALUES (0, 'hello'); \
INSERT INTO hello VALUES (1, 'world');";
db.run(sqlstr); // Run the query without returning anything

// Prepare an sql statement
const stmt = db.prepare("SELECT * FROM hello WHERE a=:aval AND b=:bval");

// Bind values to the parameters and fetch the results of the query
const result = stmt.getAsObject({':aval' : 1, ':bval' : 'world'});
console.log(result); // Will print {a:1, b:'world'}

// Bind other values
stmt.bind([0, 'hello']);
while (stmt.step()) console.log(stmt.get()); // Will print [0, 'hello']
// free the memory used by the statement
stmt.free();
// You can not use your statement anymore once it has been freed.
// But not freeing your statements causes memory leaks. You don't want that.

const res = db.exec("SELECT * FROM hello");
/*
[
  {columns:['a','b'], values:[[0,'hello'],[1,'world']]}
]
*/

// You can also use JavaScript functions inside your SQL code
// Create the js function you need
function add(a, b) {return a+b;}
// Specifies the SQL function's name, the number of it's arguments, and the js function to use
db.create_function("add_js", add);
// Run a query in which the function is used
db.run("INSERT INTO hello VALUES (add_js(7, 3), add_js('Hello ', 'world'));"); // Inserts 10 and 'Hello world'

// Export the database to an Uint8Array containing the SQLite database file
const binaryArray = db.export();
```

## Demo
There are a few examples [available here](https://sql-js.github.io/sql.js/index.html). The most full-featured is the [Sqlite Interpreter](https://sql-js.github.io/sql.js/examples/GUI/index.html).

## Examples
The test files provide up to date example of the use of the api.
### Inside the browser
#### Example **HTML** file:
```html
<meta charset="utf8" />
<html>
  <script src='/dist/sql-wasm.js'></script>
  <script>
    config = {
      locateFile: filename => `/dist/${filename}`
    }
    // The `initSqlJs` function is globally provided by all of the main dist files if loaded in the browser.
    // We must specify this locateFile function if we are loading a wasm file from anywhere other than the current html page's folder.
    initSqlJs(config).then(function(SQL){
      //Create the database
      const db = new SQL.Database();
      // Run a query without reading the results
      db.run("CREATE TABLE test (col1, col2);");
      // Insert two rows: (1,111) and (2,222)
      db.run("INSERT INTO test VALUES (?,?), (?,?)", [1,111,2,222]);

      // Prepare a statement
      const stmt = db.prepare("SELECT * FROM test WHERE col1 BETWEEN $start AND $end");
      stmt.getAsObject({$start:1, $end:1}); // {col1:1, col2:111}

      // Bind new values
      stmt.bind({$start:1, $end:2});
      while(stmt.step()) { //
        const row = stmt.getAsObject();
        console.log('Here is a row: ' + JSON.stringify(row));
      }
    });
  </script>
  <body>
    Output is in Javascript console
  </body>
</html>
```

#### Creating a database from a file chosen by the user
`SQL.Database` constructor takes an array of integer representing a database file as an optional parameter.
The following code uses an HTML input as the source for loading a database:
```javascript
dbFileElm.onchange = () => {
  const f = dbFileElm.files[0];
  const r = new FileReader();
  r.onload = function() {
    const Uints = new Uint8Array(r.result);
    db = new SQL.Database(Uints);
  }
  r.readAsArrayBuffer(f);
}
```
See : https://sql-js.github.io/sql.js/examples/GUI/gui.js

#### Loading a database from a server

##### using fetch

```javascript
const sqlPromise = initSqlJs({
  locateFile: file => `https://path/to/your/dist/folder/dist/${file}`
});
const dataPromise = fetch("/path/to/database.sqlite").then(res => res.arrayBuffer());
const [SQL, buf] = await Promise.all([sqlPromise, dataPromise])
const db = new SQL.Database(new Uint8Array(buf));
```

##### using XMLHttpRequest

```javascript
const xhr = new XMLHttpRequest();
// For example: https://github.com/lerocha/chinook-database/raw/master/ChinookDatabase/DataSources/Chinook_Sqlite.sqlite
xhr.open('GET', '/path/to/database.sqlite', true);
xhr.responseType = 'arraybuffer';

xhr.onload = e => {
  const uInt8Array = new Uint8Array(xhr.response);
  const db = new SQL.Database(uInt8Array);
  const contents = db.exec("SELECT * FROM my_table");
  // contents is now [{columns:['col1','col2',...], values:[[first row], [second row], ...]}]
};
xhr.send();
```
See: https://github.com/sql-js/sql.js/wiki/Load-a-database-from-the-server


### Use from node.js

`sql.js` is [hosted on npm](https://www.npmjs.org/package/sql.js). To install it, you can simply run `npm install sql.js`.
Alternatively, you can simply download `sql-wasm.js` and `sql-wasm.wasm`, from the download link below.

#### read a database from the disk:
```javascript
const fs = require('fs');
const initSqlJs = require('sql-wasm.js');
const filebuffer = fs.readFileSync('test.sqlite');

initSqlJs().then(function(SQL){
  // Load the db
  const db = new SQL.Database(filebuffer);
});

```

#### write a database to the disk
You need to convert the result of `db.export` to a buffer
```javascript
const fs = require("fs");
// [...] (create the database)
const data = db.export();
const buffer = new Buffer(data);
fs.writeFileSync("filename.sqlite", buffer);
```

See : https://github.com/sql-js/sql.js/blob/master/test/test_node_file.js

### Use as web worker
If you don't want to run CPU-intensive SQL queries in your main application thread,
you can use the *more limited* WebWorker API.

You will need to download `worker.sql-wasm.js` and `worker.sql-wasm.wasm` from the [release page](https://github.com/sql-js/sql.js/releases).

Example:
```html
<script>
  const worker = new Worker("/dist/worker.sql-wasm.js");
  worker.onmessage = () => {
    console.log("Database opened");
    worker.onmessage = event => {
      console.log(event.data); // The result of the query
    };

    worker.postMessage({
      id: 2,
      action: "exec",
      sql: "SELECT age,name FROM test WHERE id=$id",
      params: { "$id": 1 }
    });
  };

  worker.onerror = e => console.log("Worker error: ", e);
  worker.postMessage({
    id:1,
    action:"open",
    buffer:buf, /*Optional. An ArrayBuffer representing an SQLite Database file*/
  });
</script>
```
### Enabling BigInt support
If you need ```BigInt``` support, it is partially supported since most browsers now supports it including Safari.Binding ```BigInt``` is still not supported, only getting ```BigInt``` from the database is supported for now.

```html
<script>
  const stmt = db.prepare("SELECT * FROM test");
  const config = {useBigInt: true};
  /*Pass optional config param to the get function*/
  while (stmt.step()) console.log(stmt.get(null, config));

  /*OR*/
  const result = db.exec("SELECT * FROM test", config);
  console.log(results[0].values)
</script>
```
On WebWorker, you can just add ```config``` param before posting a message. With this, you wont have to pass config param on ```get``` function.

```html
<script>
  worker.postMessage({
    id:1,
    action:"exec",
    sql: "SELECT * FROM test",
    config: {useBigInt: true}, /*Optional param*/
  });
</script>
```

See [examples/GUI/gui.js](examples/GUI/gui.js) for a full working example.

## Flavors/versions Targets/Downloads

This library includes both WebAssembly and asm.js versions of Sqlite. (WebAssembly is the newer, preferred way to compile to JavaScript, and has superceded asm.js. It produces smaller, faster code.) Asm.js versions are included for compatibility.

## Upgrading from 0.x to 1.x

Version 1.0 of sql.js must be loaded asynchronously, whereas asm.js was able to be loaded synchronously.

So in the past, you would:
```html
<script src='js/sql.js'></script>
<script>
  const db = new SQL.Database();
  //...
</script>
```
or:
```javascript
const SQL = require('sql.js');
const db = new SQL.Database();
//...
```

Version 1.x:
```html
<script src='dist/sql-wasm.js'></script>
<script>
  initSqlJs({ locateFile: filename => `/dist/${filename}` }).then(function(SQL){
    const db = new SQL.Database();
    //...
  });
</script>
```
or:
```javascript
const initSqlJs = require('sql-wasm.js');
initSqlJs().then(function(SQL){
  const db = new SQL.Database();
  //...
});
```

`NOTHING` is now a reserved word in SQLite, whereas previously it was not. This could cause errors like `Error: near "nothing": syntax error`

### Downloading/Using: ###
Although asm.js files were distributed as a single Javascript file, WebAssembly libraries are most efficiently distributed as a pair of files, the `.js`  loader and the `.wasm` file, like `sql-wasm.js` and `sql-wasm.wasm`. The `.js` file is responsible for loading the `.wasm` file. You can find these files on our [release page](https://github.com/sql-js/sql.js/releases)




## Versions of sql.js included in the distributed artifacts
You can always find the latest published artifacts on https://github.com/sql-js/sql.js/releases/latest.

For each [release](https://github.com/sql-js/sql.js/releases/), you will find a file called `sqljs.zip` in the *release assets*. It will contain:
 - `sql-wasm.js` : The Web Assembly version of Sql.js. Minified and suitable for production. Use this. If you use this, you will need to include/ship `sql-wasm.wasm` as well.
 - `sql-wasm-debug.js` : The Web Assembly, Debug version of Sql.js. Larger, with assertions turned on. Useful for local development. You will need to include/ship `sql-wasm-debug.wasm` if you use this.
 - `sql-asm.js` : The older asm.js version of Sql.js. Slower and larger. Provided for compatibility reasons.
 - `sql-asm-memory-growth.js` : Asm.js doesn't allow for memory to grow by default, because it is slower and de-optimizes. If you are using sql-asm.js and you see this error (`Cannot enlarge memory arrays`), use this file.
 - `sql-asm-debug.js` : The _Debug_ asm.js version of Sql.js. Use this for local development.
 - `worker.*` - Web Worker versions of the above libraries. More limited API. See [examples/GUI/gui.js](examples/GUI/gui.js) for a good example of this.

## Compiling/Contributing

General consumers of this library don't need to read any further. (The compiled files are available via the [release page](https://github.com/sql-js/sql.js/releases).)

If you want to compile your own version of SQLite for WebAssembly, or want to contribute to this project, see [CONTRIBUTING.md](CONTRIBUTING.md).