docs.sheetjs.com/docz/docs/03-demos/01-frontend/01-react.md

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title: ReactJS
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import Tabs from '@theme/Tabs';
import TabItem from '@theme/TabItem';
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ReactJS is a JS library for building user interfaces.

This demo tries to cover common React data flow ideas and strategies. React
familiarity is assumed.

Other demos cover general React deployments, including:

- [Static Site Generation powered by NextJS](/docs/demos/static/nextjs)
- [iOS and Android applications powered by React Native](/docs/demos/mobile/reactnative)
- [Desktop application powered by React Native Windows + macOS](/docs/demos/desktop/reactnative)
- [React Data Grid UI component](/docs/demos/grid/rdg)
- [Glide Data Grid UI component](/docs/demos/grid/gdg)


## Installation

[The "Frameworks" section](/docs/getting-started/installation/frameworks) covers
installation with Yarn and other package managers.

The library can be imported directly from JS or JSX code with:

```js
import { read, utils, writeFile } from 'xlsx';
```


## Internal State

The various SheetJS APIs work with various data shapes.  The preferred state
depends on the application.

### Array of Objects

Typically, some users will create a spreadsheet with source data that should be
loaded into the site.  This sheet will have known columns.

#### State

The example [presidents sheet](https://sheetjs.com/pres.xlsx) has one header row
with "Name" and "Index" columns. The natural JS representation is an object for
each row, using the values in the first rows as keys:

<table><thead><tr><th>Spreadsheet</th><th>State</th></tr></thead><tbody><tr><td>

![`pres.xlsx` data](pathname:///pres.png)

</td><td>

```js
[
  { Name: "Bill Clinton", Index: 42 },
  { Name: "GeorgeW Bush", Index: 43 },
  { Name: "Barack Obama", Index: 44 },
  { Name: "Donald Trump", Index: 45 },
  { Name: "Joseph Biden", Index: 46 }
]
```

</td></tr></tbody></table>

The React `useState` hook can configure the state:

<Tabs groupId="lang">
  <TabItem name="JS" value="JavaScript">

```ts
import { useState } from 'react';

/* the component state is an array of presidents */
const [pres, setPres] = useState([]);
```

  </TabItem>
  <TabItem name="TS" value="TypeScript" default>

```ts
import { useState } from 'react';

interface President {
  Name: string;
  Index: number;
}

/* the component state is an array of presidents */
const [pres, setPres] = useState<President[]>([]);
```

:::note

The types are informative. They do not enforce that worksheets include the named
columns. A runtime data validation library should be used to verify the dataset.

:::

  </TabItem>
</Tabs>

#### Updating State

The [`read`](/docs/api/parse-options) and [`sheet_to_json`](/docs/api/utilities/array#array-output)
functions simplify state updates. They are best used in the function bodies of
`useEffect` and `useCallback` hooks.

A `useEffect` hook can download and update state when a person loads the site:

```mermaid
flowchart LR
  url[(Remote\nFile)]
  ab[(Data\nArrayBuffer)]
  wb(SheetJS\nWorkbook)
  ws(SheetJS\nWorksheet)
  aoo(array of\nobjects)
  state((component\nstate))
  url --> |fetch\n\n| ab
  ab --> |read\n\n| wb
  wb --> |wb.Sheets\nselect sheet| ws
  ws --> |sheet_to_json\n\n| aoo
  aoo --> |setPres\nfrom `setState`| state
```

<Tabs groupId="lang">
  <TabItem name="JS" value="JavaScript">

```ts
import { useEffect } from 'react';
import { read, utils } from 'xlsx';

/* Fetch and update the state once */
useEffect(() => { (async() => {
  /* Download file */
  const f = await (await fetch("https://sheetjs.com/pres.xlsx")).arrayBuffer();
  // highlight-start
  const wb = read(f); // parse the array buffer
  const ws = wb.Sheets[wb.SheetNames[0]]; // get the first worksheet
  const data = utils.sheet_to_json(ws); // generate objects
  setPres(data); // update state
  // highlight-end
})(); }, []);
```

  </TabItem>
  <TabItem name="TS" value="TypeScript" default>

```ts
import { useEffect } from 'react';
import { read, utils } from 'xlsx';

/* Fetch and update the state once */
useEffect(() => { (async() => {
  /* Download file */
  const f = await (await fetch("https://sheetjs.com/pres.xlsx")).arrayBuffer();
  // highlight-start
  const wb = read(f); // parse the array buffer
  const ws = wb.Sheets[wb.SheetNames[0]]; // get the first worksheet
  const data: President[] = utils.sheet_to_json<President>(ws); // generate objects
  setPres(data); // update state
  // highlight-end
})(); }, []);
```

  </TabItem>
</Tabs>

#### Rendering Data

Components typically render HTML tables from arrays of objects. The `<tr>` table
row elements are typically generated by mapping over the state array, as shown
in the example JSX code:

```jsx title="Example JSX for displaying arrays of objects"
<table>
  {/* The `thead` section includes the table header row */}
  <thead><th>Name</th><th>Index</th></thead>
  {/* The `tbody` section includes the data rows */}
  <tbody>
    {/* generate row (TR) for each president */}
// highlight-start
    {pres.map(row => (
      <tr>
        {/* Generate cell (TD) for name / index */}
        <td>{row.Name}</td>
        <td>{row.Index}</td>
      </tr>
    ))}
// highlight-end
  </tbody>
</table>
```

#### Exporting Data

The [`writeFile`](/docs/api/write-options) and [`json_to_sheet`](/docs/api/utilities/array#array-of-objects-input)
functions simplify exporting data. They are best used in the function bodies of
`useCallback` hooks attached to button or other elements.

A callback can generate a local file when a user clicks a button:

```mermaid
flowchart LR
  state((component\nstate))
  ws(SheetJS\nWorksheet)
  wb(SheetJS\nWorkbook)
  file[(XLSX\nexport)]
  state --> |json_to_sheet\n\n| ws
  ws --> |book_new\nbook_append_sheet| wb
  wb --> |writeFile\n\n| file
```

```ts
import { useCallback } from 'react';
import { utils, writeFile } from 'xlsx';

/* get state data and export to XLSX */
const exportFile = useCallback(() => {
  /* generate worksheet from state */
  // highlight-next-line
  const ws = utils.json_to_sheet(pres);
  /* create workbook and append worksheet */
  const wb = utils.book_new();
  utils.book_append_sheet(wb, ws, "Data");
  /* export to XLSX */
  writeFile(wb, "SheetJSReactAoO.xlsx");
}, [pres]);
```

#### Complete Component

This complete component example fetches a test file and displays the contents in
a HTML table. When the export button is clicked, a callback will export a file:

```jsx title="src/SheetJSReactAoO.js"
import React, { useCallback, useEffect, useState } from "react";
import { read, utils, writeFileXLSX } from 'xlsx';

export default function SheetJSReactAoO() {
  /* the component state is an array of presidents */
  const [pres, setPres] = useState([]);

  /* Fetch and update the state once */
  useEffect(() => { (async() => {
    const f = await (await fetch("https://sheetjs.com/pres.xlsx")).arrayBuffer();
    // highlight-start
    const wb = read(f); // parse the array buffer
    const ws = wb.Sheets[wb.SheetNames[0]]; // get the first worksheet
    const data = utils.sheet_to_json(ws); // generate objects
    setPres(data); // update state
    // highlight-end
  })(); }, []);

  /* get state data and export to XLSX */
  const exportFile = useCallback(() => {
    // highlight-next-line
    const ws = utils.json_to_sheet(pres);
    const wb = utils.book_new();
    utils.book_append_sheet(wb, ws, "Data");
    writeFileXLSX(wb, "SheetJSReactAoO.xlsx");
  }, [pres]);

  return (<table><thead><th>Name</th><th>Index</th></thead><tbody>
    { /* generate row for each president */
// highlight-start
      pres.map(pres => (<tr>
        <td>{pres.Name}</td>
        <td>{pres.Index}</td>
      </tr>))
// highlight-end
    }
  </tbody><tfoot><td colSpan={2}>
    <button onClick={exportFile}>Export XLSX</button>
  </td></tfoot></table>);
}
```

<details open><summary><b>How to run the example</b> (click to show)</summary>

:::note

This demo was last run on 2023 February 28 using `create-react-app@5.0.1` and
`react-scripts@5.0.1`.

:::

1) Run `npx create-react-app@5.0.1 --scripts-version=5.0.1 sheetjs-react`.

2) Install the SheetJS dependency and start the dev server:

<CodeBlock language="bash">{`\
cd sheetjs-react
npm i
npm i --save https://cdn.sheetjs.com/xlsx-${current}/xlsx-${current}.tgz
npm start`}
</CodeBlock>

3) Open a web browser and access the displayed URL (`http://localhost:3000`)

4) Replace `src/App.js` with the `src/SheetJSReactAoO.js` example.

The page will refresh and show a table with an Export button.  Click the button
and the page will attempt to download `SheetJSReactAoA.xlsx`.

5) Build the site with `npm run build`, then test with `npx http-server build`.
Access `http://localhost:8080` with a web browser to test the bundled site.

</details>

### HTML

The main disadvantage of the Array of Objects approach is the specific nature
of the columns.  For more general use, passing around an Array of Arrays works.
However, this does not handle merge cells well!

The `sheet_to_html` function generates HTML that is aware of merges and other
worksheet features.  React `dangerouslySetInnerHTML` attribute allows code to
set the `innerHTML` attribute, effectively inserting the code into the page.

In this example, the component attaches a `ref` to the `DIV` container. During
export, the first `TABLE` child element can be parsed with `table_to_book` to
generate a workbook object.

```jsx title="src/SheetJSReactHTML.js"
import React, { useCallback, useEffect, useRef, useState } from "react";
import { read, utils, writeFileXLSX } from 'xlsx';

export default function SheetJSReactHTML() {
  /* the component state is an HTML string */
  const [__html, setHtml] = useState("");
  /* the ref is used in export */
  const tbl = useRef(null);

  /* Fetch and update the state once */
  useEffect(() => { (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
    // highlight-start
    const data = utils.sheet_to_html(ws); // generate HTML
    setHtml(data); // update state
    // highlight-end
  })(); }, []);

  /* get live table and export to XLSX */
  const exportFile = useCallback(() => {
    // highlight-start
    const elt = tbl.current.getElementsByTagName("TABLE")[0];
    const wb = utils.table_to_book(elt);
    // highlight-end
    writeFileXLSX(wb, "SheetJSReactHTML.xlsx");
  }, [tbl]);

  return ( <>
    <button onClick={exportFile}>Export XLSX</button>
  // highlight-next-line
    <div ref={tbl} dangerouslySetInnerHTML={{ __html }} />
  </> );
}
```

<details open><summary><b>How to run the example</b> (click to show)</summary>

:::note

This demo was last run on 2023 February 28 using `create-react-app@5.0.1` and
`react-scripts@5.0.1`.

:::

1) Run `npx create-react-app@5.0.1 --scripts-version=5.0.1 sheetjs-react`.

2) Install the SheetJS dependency and start the dev server:

<CodeBlock language="bash">{`\
cd sheetjs-react
npm i
npm i --save https://cdn.sheetjs.com/xlsx-${current}/xlsx-${current}.tgz
npm start`}
</CodeBlock>

3) Open a web browser and access the displayed URL (`http://localhost:3000`)

4) Replace `src/App.js` with the `src/SheetJSReactHTML.js` example.

The page will refresh and show a table with an Export button.  Click the button
and the page will attempt to download `SheetJSReactHTML.xlsx`.

5) Build the site with `npm run build`, then test with `npx http-server build`.
Access `http://localhost:8080` with a web browser to test the bundled site.

</details>

### Rows and Columns

Some data grids and UI components split worksheet state in two parts: an array
of column attribute objects and an array of row objects.  The former is used to
generate column headings and for indexing into the row objects.

The safest approach is to use an array of arrays for state and to generate
column objects that map to A1-Style column headers.

The [React Data Grid demo](/docs/demos/grid#rows-and-columns-state) uses this approach
with the following column and row structure:

```js
/* rows are generated with a simple array of arrays */
const rows = utils.sheet_to_json(worksheet, { header: 1 });

/* column objects are generated based on the worksheet range */
const range = utils.decode_range(ws["!ref"]||"A1");
const columns = Array.from({ length: range.e.c + 1 }, (_, i) => ({
  /* for an array of arrays, the keys are "0", "1", "2", ... */
  key: String(i),
  /* column labels: encode_col translates 0 -> "A", 1 -> "B", 2 -> "C", ... */
  name: XLSX.utils.encode_col(i)
}));

```

![Column labels for headers](pathname:///react/cols.png)



## Legacy Deployments

[The Standalone Scripts](/docs/getting-started/installation/standalone) play nice
with legacy deployments that do not use a bundler.

[The legacy demo](pathname:///react/index.html) shows a simple React component
transpiled in the browser using Babel standalone library.