---
title: NeutralinoJS
pagination_prev: demos/mobile/index
pagination_next: demos/data/index
sidebar_position: 5
sidebar_custom_props:
summary: Webview + Lightweight Extensions
---
import current from '/version.js';
import Tabs from '@theme/Tabs';
import TabItem from '@theme/TabItem';
import CodeBlock from '@theme/CodeBlock';
The [Standalone build](/docs/getting-started/installation/standalone) can be added
to the entry `index.html`
The "Complete Example" creates an app that looks like the screenshot:
## Integration Details
:::note
NeutralinoJS currently does not provide the equivalent of NodeJS `fs` module.
The raw `Neutralino.filesystem` and `Neutralino.os` methods are used.
:::
The `os` and `filesystem` modules must be enabled in `neutralino.conf.json`.
The starter already enables `os` so typically one line must be added:
```json title="neutralino.config.json"
"nativeAllowList": [
"app.*",
"os.*",
// highlight-next-line
"filesystem.*",
"debug.log"
],
```
:::caution
At the time of writing, `filters` did not work as expected on MacOS. They have
been omitted in the example and commented in the code snippets
:::
### Reading Files
There are two steps to reading files: obtaining a path and reading binary data:
```js
const filters = [
{name: "Excel Binary Workbook", extensions: ["xlsb"]},
{name: "Excel Workbook", extensions: ["xlsx"]},
]
async function openFile() {
/* show open file dialog */
const [filename] = await Neutralino.os.showOpenDialog(
'Open a spreadsheet',
{ /* filters, */ multiSelections: false }
);
/* read data into an ArrayBuffer */
const ab = await Neutralino.filesystem.readBinaryFile(filename);
/* parse with SheetJS */
const wb = XLSX.read(ab);
return wb;
}
```
This method can be called from a button click or other event.
### Writing Files
There are two steps to writing files: obtaining a path and writing binary data:
```js
const filters = [
{name: "Excel Binary Workbook", extensions: ["xlsb"]},
{name: "Excel Workbook", extensions: ["xlsx"]},
]
async function saveFile(wb) {
/* show save file dialog */
const filename = await Neutralino.os.showSaveDialog(
'Save to file',
{ /* filters */ }
);
/* Generate workbook */
const bookType = filename.slice(filename.lastIndexOf(".") + 1);
const data = XLSX.write(wb, { bookType, type: "buffer" });
/* save data to file */
await Neutralino.filesystem.writeBinaryFile(filename, data);
}
```
## Complete Example
:::note
This demo was tested on 2023 March 19 with "binaries" `4.7.0` and "client" `3.6.0`
:::
The app core state will be the HTML table. Reading files will add the table to
the window. Writing files will parse the table into a spreadsheet.
1) Create a new NeutralinoJS app:
```bash
npx @neutralinojs/neu create sheetjs-neu
cd sheetjs-neu
```
2) Download [Standalone build](/docs/getting-started/installation/standalone)
and place in `resources/js/main.js`:
{`\
curl -L -o resources/js/xlsx.full.min.js https://cdn.sheetjs.com/xlsx-${current}/package/dist/xlsx.full.min.js`}
3) Add the highlighted line to `neutralino.conf.json` in `nativeAllowList`:
```json title="neutralino.config.json"
"nativeAllowList": [
"app.*",
"os.*",
// highlight-start
"filesystem.*",
// highlight-end
"debug.log"
],
```
4) Set up skeleton app and print version info:
- Edit `resources/index.html` and replace the `` with the code below:
```html title="resources/index.html"
SheetJS × NeutralinoJS
```
- Append the following code to `resources/styles.css` to center the table:
```css title="resources/styles.css"
#info {
width:100%;
text-align: unset;
}
table {
margin: 0 auto;
}
```
- Print the version number in the `showInfo` method of `resources/js/main.js`:
```js title="resources/js/main.js"
${NL_APPID} is running on port ${NL_PORT} inside ${NL_OS}
SheetJS version ${XLSX.version}
// highlight-end
`;
```
5) Run the app:
```bash
npx @neutralinojs/neu run
```
You should see `SheetJS Version ` followed by the library version number.
6) Add the following code to the bottom of `resources/js/main.js`:
```js
(async() => {
const ab = await (await fetch("https://sheetjs.com/pres.numbers")).arrayBuffer();
const wb = XLSX.read(ab);
const ws = wb.Sheets[wb.SheetNames[0]];
document.getElementById('info').innerHTML = XLSX.utils.sheet_to_html(ws);
})();
```
Save the source file, close the app and re-run the command from step 5.
When the app loads, a table should show in the main screen.
7) Add `importFile` and `exportFile` to the bottom of `resources/js/main.js`:
```js
async function importData() {
/* show open dialog */
const [filename] = await Neutralino.os.showOpenDialog('Open a spreadsheet');
/* read data */
const ab = await Neutralino.filesystem.readBinaryFile(filename);
const wb = XLSX.read(ab);
/* make table */
const ws = wb.Sheets[wb.SheetNames[0]];
document.getElementById('info').innerHTML = XLSX.utils.sheet_to_html(ws);
}
async function exportData() {
/* show save dialog */
const filename = await Neutralino.os.showSaveDialog('Save to file');
/* make workbook */
const tbl = document.getElementById('info').querySelector("table");
const wb = XLSX.utils.table_to_book(tbl);
/* make file */
const bookType = filename.slice(filename.lastIndexOf(".") + 1);
const data = XLSX.write(wb, { bookType, type: "buffer" });
await Neutralino.filesystem.writeBinaryFile(filename, data);
}
```
Save the source file, close the app and re-run the command from step 5.
When the app loads, click the "Import File" button and select a spreadsheet to
see the contents. Click "Export File" and enter `SheetJSNeu.xlsx` to write.
8) Build production apps:
```bash
npx @neutralinojs/neu run
```
Platform-specific programs will be created in the `dist` folder.