---
title: CapacitorJS
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sidebar_position: 5
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  summary: JS + Web View
---

## CapacitorJS

:::note

This demo was tested on an Intel Mac on 2022 August 26 with Svelte.

The iOS simulator runs iOS 15.5 on an iPhone 13 Pro Max.

:::

:::warning Telemetry

Before starting this demo, manually disable telemetry.  On Linux and MacOS:

```bash
npx @capacitor/cli telemetry off
```

To verify telemetry was disabled:

```bash
npx @capacitor/cli telemetry
```

:::

### Integration Details

This example uses Svelte, but the same principles apply to other frameworks.

#### Reading data

The standard HTML5 File Input element logic works in CapacitorJS:

```html
<script>
import { read, utils } from 'xlsx';

let html = "";

/* show file picker, read file, load table */
async function importFile(evt) {
  // highlight-start
  const f = evt.target.files[0];
  const wb = read(await f.arrayBuffer());
  // highlight-end
  const ws = wb.Sheets[wb.SheetNames[0]]; // get the first worksheet
  html = utils.sheet_to_html(ws); // generate HTML and update state
}
</script>

<main>
  <!-- highlight-next-line -->
  <input type="file" on:change={importFile}/>
  <div bind:this={tbl}>{@html html}</div>
</main>
```

#### Writing data

`@capacitor/filesystem` can write Base64 strings:

```html
<script>
import { Filesystem, Directory } from '@capacitor/filesystem';
import { utils, writeXLSX } from 'xlsx';

let html = "";
let tbl;

/* get state data and export to XLSX */
async function exportFile() {
  const elt = tbl.getElementsByTagName("TABLE")[0];
  const wb = utils.table_to_book(elt);
  /* generate Base64 string for Capacitor */
  // highlight-start
  const data = writeXLSX(wb, { type: "base64" });
  await Filesystem.writeFile({
    data,
    path: "SheetJSCap.xlsx",
    directory: Directory.Documents
  }); // write file
  // highlight-end
}

</script>

<main>
  <button on:click={exportFile}>Export XLSX</button>
  <div bind:this={tbl}>{@html html}</div>
</main>
```

### Demo

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

0) Disable telemetry as noted in the warning.

Follow the [React Native demo](#demo) to ensure iOS and Android sims are ready.


1) Create a new Svelte project:

```bash
npm create vite@latest sheetjs-cap -- --template svelte
cd sheetjs-cap
```

2) Install dependencies:

```bash
npm i --save https://cdn.sheetjs.com/xlsx-latest/xlsx-latest.tgz
npm i --save @capacitor/core @capacitor/cli @capacitor/ios @capacitor/filesystem
```

3) Create CapacitorJS structure:

```bash
npx cap init sheetjs-cap com.sheetjs.cap --web-dir=dist
npx cap add ios
```

4) Replace the contents of `src/App.svelte` with the following:

```html title="src/App.svelte"
<script>
import { Filesystem, Directory, Encoding } from '@capacitor/filesystem';
import { onMount } from 'svelte';
import { read, utils, version, writeXLSX } from 'xlsx';

let html = "";
let tbl;

/* Fetch and update the state once */
onMount(async() => {
  const f = await (await fetch("https://sheetjs.com/pres.xlsx")).arrayBuffer();
  const wb = read(f); // parse the array buffer
  const ws = wb.Sheets[wb.SheetNames[0]]; // get the first worksheet
  html = utils.sheet_to_html(ws); // generate HTML and update state
});

/* get state data and export to XLSX */
async function exportFile() {
  const elt = tbl.getElementsByTagName("TABLE")[0];
  const wb = utils.table_to_book(elt);
  /* generate Base64 string for Capacitor */
  const data = writeXLSX(wb, { type: "base64" });
  /* write */
  await Filesystem.writeFile({
    path: "SheetJSCap.xlsx",
    data,
    directory: Directory.Documents
  });
}

/* show file picker, read file, load table */
async function importFile(evt) {
  const f = evt.target.files[0];
  const wb = read(await f.arrayBuffer());
  const ws = wb.Sheets[wb.SheetNames[0]]; // get the first worksheet
  html = utils.sheet_to_html(ws); // generate HTML and update state
}
</script>

<main>
  <h3>SheetJS × CapacitorJS { version }</h3>
  <input type="file" on:change={importFile}/>
  <button on:click={exportFile}>Export XLSX</button>
  <div bind:this={tbl}>{@html html}</div>
</main>
```

5) Test the app:

```bash
npm run build; npx cap sync; npx cap run ios
```

There are 3 steps: build the Svelte app, sync with CapacitorJS, and run sim.
This sequence must be run every time to ensure changes are propagated.

</details>