docs.sheetjs.com/docz/docs/04-getting-started/03-demos/16-desktop.md

---
sidebar_position: 16
title: Desktop Applications
---

Web technologies like JavaScript and HTML have been adapted to the traditional
app space.  Typically these frameworks bundle a JavaScript engine as well as a
windowing framework. SheetJS is compatible with many toolkits.

## NW.js

The [Standalone scripts](../../installation/standalone) can be referenced in a
`SCRIPT` tag from the entry point HTML page.

This demo was tested against NW.js 0.66.0.

<details><summary><b>Complete Example</b> (click to show)</summary>

1) Create a `package.json` file that specifies the entry point:

```json title="package.json"
{
  "name": "sheetjs-nwjs",
  "author": "sheetjs",
  "version": "0.0.0",
  "main": "index.html",
  "dependencies": {
    "nw": "~0.66.0",
    "xlsx": "https://cdn.sheetjs.com/xlsx-latest/xlsx-latest.tgz"
  }
}
```

2) Download [`index.html`](pathname:///nwjs/index.html) into the same folder.

:::caution

Right-click the link and select "Save Link As...".  Left-clicking the link will
try to load the page in your browser.  The goal is to save the file contents.

:::

3) Run `npm install` to install dependencies

4) To verify the app works, run in the test environment:

```
npx nw .
```

The app will show and you should be able to verify reading and writing by using
the file input element to select a spreadsheet and clicking the export button.

5) To build a standalone app, run the builder:

```
npx -p nw-builder nwbuild --mode=build .
```

This will generate the standalone app in the `build\sheetjs-nwjs\` folder.

</details>

### Reading data

The standard HTML5 `FileReader` techniques from the browser apply to NW.js!

NW.js handles the OS minutiae for dragging files into app windows.  The
[drag and drop snippet](../../solutions/input#example-user-submissions) apply
to DIV elements on the page.

Similarly, file input elements automatically map to standard Web APIs.

For example, assuming a file input element on the page:

```html
<input type="file" name="xlfile" id="xlf" /> 
```

The event handler would process the event as if it were a web event:

```js
async function handleFile(e) {
  const file = e.target.files[0];
  const data = await file.arrayBuffer();
  /* data is an ArrayBuffer */
  const workbook = XLSX.read(data);

  /* DO SOMETHING WITH workbook HERE */
}
document.getElementById("xlf").addEventListener("change", handleFile, false);
```

### Writing data

File input elements with the attribute `nwsaveas` show UI for saving a file. The
standard trick is to generate a hidden file input DOM element and "click" it.
Since NW.js does not present a `writeFileSync` in the `fs` package, a manual
step is required:

```js
/* pre-build the hidden nwsaveas input element */
var input = document.createElement('input');
input.style.display = 'none';
input.setAttribute('nwsaveas', 'SheetJSNWDemo.xlsx');
input.setAttribute('type', 'file');
document.body.appendChild(input);

/* show a message if the save is canceled */
input.addEventListener('cancel',function(){ alert("Save was canceled!"); });

/* write to a file on the 'change' event */
input.addEventListener('change',function(e){
  /* the `value` is the path that the program will write */
  var filename = this.value;

  /* use XLSX.write with type "buffer" to generate a buffer" */
  /* highlight-next-line */
  var wbout = XLSX.write(workbook, {type:'buffer', bookType:"xlsx"});
  /* highlight-next-line */
  fs.writeFile(filename, wbout, function(err) {
    if(!err) return alert("Saved to " + filename);
    alert("Error: " + (err.message || err));
  });
});

input.click();
```

## Electron

The [NodeJS Module](../../installation/nodejs) can be imported from the main or
the renderer thread.

Electron presents a `fs` module.  The `require('xlsx')` call loads the CommonJS
module, so `XLSX.readFile` and `XLSX.writeFile` work in the renderer thread.

This demo was tested against Electron 19.0.5 on an Intel Mac (`darwin-x64`).

<details><summary><b>Complete Example</b> (click to show)</summary>

This demo includes a drag-and-drop box as well as a file input box, mirroring
the [SheetJS Data Preview Live Demo](http://oss.sheetjs.com/sheetjs/)

The core data in this demo is an editable HTML table.  The readers build up the
table using `sheet_to_html` (with `editable:true` option) and the writers scrape
the table using `table_to_book`.

The demo project is wired for `electron-forge` to build the standalone binary.

1) Download the demo files:

- [`package.json`](pathname:///electron/package.json) : project structure
- [`main.js`](pathname:///electron/main.js) : entrypoint
- [`index.html`](pathname:///electron/index.html) : window page
- [`index.js`](pathname:///electron/index.js) : script loaded in render context

:::caution

Right-click each link and select "Save Link As...".  Left-clicking a link will
try to load the page in your browser.  The goal is to save the file contents.

:::

2) Run `npm install` to install dependencies.

3) To verify the app works, run in the test environment:

```bash
npx -y electron .
```

The app will show and you should be able to verify reading and writing by using
the relevant buttons to open files and clicking the export button.

4) To build a standalone app, run the builder:

```bash
npm run make
```

This will generate the standalone app in the `out\sheetjs-electron-...` folder.
For a recent Intel Mac, the path will be `out/sheetjs-electron-darwin-x64/`

</details>

### Writing Files

[`XLSX.writeFile`](../../api/write-options) writes workbooks to the filesystem.
`showSaveDialog` shows a Save As dialog and returns the selected file name:

```js
/* from the renderer thread */
const electron = require('@electron/remote');

/* this function will show the save dialog and try to write the workbook */
async function exportFile(workbook) {
  /* show Save As dialog */
  const result = await electron.dialog.showSaveDialog({
    title: 'Save file as',
    filters: [{
      name: "Spreadsheets",
      extensions: ["xlsx", "xls", "xlsb", /* ... other formats ... */]
    }]
  });
  /* write file */
  // highlight-next-line
  XLSX.writeFile(workbook, result.filePath);
}
```

:::note

In older versions of Electron, `showSaveDialog` returned the path directly:

```js
var dialog = require('electron').remote.dialog;

function exportFile(workbook) {
  var result = dialog.showSaveDialog();
  XLSX.writeFile(workbook, result);
}
```

:::

### Reading Files

Electron offers 3 different ways to read files, two of which use Web APIs.

**File Input Element**

File input elements automatically map to standard Web APIs.

For example, assuming a file input element on the page:

```html
<input type="file" name="xlfile" id="xlf" /> 
```

The event handler would process the event as if it were a web event:

```js
async function handleFile(e) {
  const file = e.target.files[0];
  const data = await file.arrayBuffer();
  /* data is an ArrayBuffer */
  const workbook = XLSX.read(data);

  /* DO SOMETHING WITH workbook HERE */
}
document.getElementById("xlf").addEventListener("change", handleFile, false);
```

**Drag and Drop**

The [drag and drop snippet](../../solutions/input#example-user-submissions)
applies to DIV elements on the page.

For example, assuming a DIV on the page:

```html
<div id="drop">Drop a spreadsheet file here to see sheet data</div>
```

The event handler would process the event as if it were a web event:

```js
async function handleDrop(e) {
  e.stopPropagation();
  e.preventDefault();

  const file = e.dataTransfer.files[0];
  const data = await file.arrayBuffer();
  /* data is an ArrayBuffer */
  const workbook = XLSX.read(data);

  /* DO SOMETHING WITH workbook HERE */
}
document.getElementById("drop").addEventListener("drop", handleDrop, false);
```

**Electron API**

[`XLSX.readFile`](../../api/parse-options) reads workbooks from the filesystem.
`showOpenDialog` shows a Save As dialog and returns the selected file name.
Unlike the Web APIs, the `showOpenDialog` flow can be initiated by app code:

```js
/* from the renderer thread */
const electron = require('@electron/remote');

/* this function will show the open dialog and try to parse the workbook */
async function importFile() {
  /* show Save As dialog */
  const result = await electron.dialog.showOpenDialog({
    title: 'Select a file',
    filters: [{
      name: "Spreadsheets",
      extensions: ["xlsx", "xls", "xlsb", /* ... other formats ... */]
    }]
  });
  /* result.filePaths is an array of selected files */
  if(result.filePaths.length == 0) throw new Error("No file was selected!");
  // highlight-next-line
  return XLSX.readFile(result.filePaths[0]);
}
```

:::note

In older versions of Electron, `showOpenDialog` returned the path directly:

```js
var dialog = require('electron').remote.dialog;

function importFile(workbook) {
  var result = dialog.showOpenDialog({ properties: ['openFile'] });
  return XLSX.readFile(result[0]);
}
```

:::

### Electron Breaking Changes

The first version of this demo used Electron 1.7.5.  The current demo includes
the required changes for Electron 19.0.5.

There are no Electron-specific workarounds in the library, but Electron broke
backwards compatibility multiple times.  A summary of changes is noted below.

:::caution

Electron 6.x changed the `dialog` API. Methods like `showSaveDialog` originally
returned an array of strings, but now returns a `Promise`.  This change was not
documented. [Electron issue](https://github.com/electron/electron/issues/24438)

Electron 9.0.0 and later require the preference `nodeIntegration: true` in order
to `require('xlsx')` in the renderer process.

Electron 12.0.0 and later also require `worldSafeExecuteJavascript: true` and
`contextIsolation: true`.

Electron 14+ must use `@electron/remote` instead of `remote`.  An `initialize`
call is required to enable DevTools in the window.

:::