xsheetjs/docbits/22_ingress.md

### Processing JSON and JS Data

JSON and JS data tend to represent single worksheets.  This section will use a
few utility functions to generate workbooks:

_Create a new Worksheet_

```js
var workbook = XLSX.utils.book_new();
```

The `book_new` utility function creates an empty workbook with no worksheets.


_Append a Worksheet to a Workbook_

```js
XLSX.utils.book_append_sheet(workbook, worksheet, sheet_name);
```

The `book_append_sheet` utility function appends a worksheet to the workbook.
The third argument specifies the desired worksheet name. Multiple worksheets can
be added to a workbook by calling the function multiple times.


**API**

_Create a worksheet from an array of arrays of JS values_

```js
var worksheet = XLSX.utils.aoa_to_sheet(aoa, opts);
```

The `aoa_to_sheet` utility function walks an "array of arrays" in row-major
order, generating a worksheet object.  The following snippet generates a sheet
with cell `A1` set to the string `A1`, cell `B1` set to `B2`, etc:

```js
var worksheet = XLSX.utils.aoa_to_sheet([
  ["A1", "B1", "C1"],
  ["A2", "B2", "C2"],
  ["A3", "B3", "C3"]
])
```

["Array of Arrays Input"](#array-of-arrays-input) describes the function and the
optional `opts` argument in more detail.


_Create a worksheet from an array of JS objects_

```js
var worksheet = XLSX.utils.json_to_sheet(jsa, opts);
```

The `json_to_sheet` utility function walks an array of JS objects in order,
generating a worksheet object.  By default, it will generate a header row and
one row per object in the array.  The optional `opts` argument has settings to
control the column order and header output.

["Array of Objects Input"](#array-of-arrays-input) describes the function and
the optional `opts` argument in more detail.

**Examples**

["Zen of SheetJS"](#the-zen-of-sheetjs) contains a detailed example "Get Data
from a JSON Endpoint and Generate a Workbook"


[`x-spreadsheet`](https://github.com/myliang/x-spreadsheet) is an interactive
data grid for previewing and modifying structured data in the web browser.  The
[`xspreadsheet` demo](/demos/xspreadsheet) includes a sample script with the
`xtos` function for converting from x-spreadsheet data object to a workbook.
<https://oss.sheetjs.com/sheetjs/x-spreadsheet> is a live demo.

<details>
  <summary><b>Records from a database query (SQL or no-SQL)</b> (click to show)</summary>

The [`database` demo](/demos/database/) includes examples of working with
databases and query results.

</details>


<details>
  <summary><b>Numerical Computations with TensorFlow.js</b> (click to show)</summary>

[`@tensorflow/tfjs`](@tensorflow/tfjs) and other libraries expect data in simple
arrays, well-suited for worksheets where each column is a data vector.  That is
the transpose of how most people use spreadsheets, where each row is a vector.

When recovering data from `tfjs`, the returned data points are stored in a typed
array.  An array of arrays can be constructed with loops. `Array#unshift` can
prepend a title row before the conversion:

```js
const XLSX = require("xlsx");
const tf = require('@tensorflow/tfjs');

/* suppose xs and ys are vectors (1D tensors) -> tfarr will be a typed array */
const tfdata = tf.stack([xs, ys]).transpose();
const shape = tfdata.shape;
const tfarr = tfdata.dataSync();

/* construct the array of arrays */
const aoa = [];
for(let j = 0; j < shape[0]; ++j) {
  aoa[j] = [];
  for(let i = 0; i < shape[1]; ++i) aoa[j][i] = tfarr[j * shape[1] + i];
}
/* add headers to the top */
aoa.unshift(["x", "y"]);

/* generate worksheet */
const worksheet = XLSX.utils.aoa_to_sheet(aoa);
```

The [`array` demo](demos/array/) shows a complete example.

</details>


### Processing HTML Tables

**API**

_Create a worksheet by scraping an HTML TABLE in the page_

```js
var worksheet = XLSX.utils.table_to_sheet(dom_element, opts);
```

The `table_to_sheet` utility function takes a DOM TABLE element and iterates
through the rows to generate a worksheet.  The `opts` argument is optional.
["HTML Table Input"](#html-table-input) describes the function in more detail.



_Create a workbook by scraping an HTML TABLE in the page_

```js
var workbook = XLSX.utils.table_to_book(dom_element, opts);
```

The `table_to_book` utility function follows the same logic as `table_to_sheet`.
After generating a worksheet, it creates a blank workbook and appends the
spreadsheet.

The options argument supports the same options as `table_to_sheet`, with the
addition of a `sheet` property to control the worksheet name.  If the property
is missing or no options are specified, the default name `Sheet1` is used.

**Examples**

Here are a few common scenarios (click on each subtitle to see the code):

<details>
  <summary><b>HTML TABLE element in a webpage</b> (click to show)</summary>

```html
<!-- include the standalone script and shim.  this uses the UNPKG CDN -->
<script src="https://unpkg.com/xlsx/dist/shim.min.js"></script>
<script src="https://unpkg.com/xlsx/dist/xlsx.full.min.js"></script>

<!-- example table with id attribute -->
<table id="tableau">
  <tr><td>Sheet</td><td>JS</td></tr>
  <tr><td>12345</td><td>67</td></tr>
</table>

<!-- this block should appear after the table HTML and the standalone script -->
<script type="text/javascript">
  var workbook = XLSX.utils.table_to_book(document.getElementById("tableau"));

  /* DO SOMETHING WITH workbook HERE */
</script>
```

Multiple tables on a web page can be converted to individual worksheets:

```js
/* create new workbook */
var workbook = XLSX.utils.book_new();

/* convert table "table1" to worksheet named "Sheet1" */
var sheet1 = XLSX.utils.table_to_sheet(document.getElementById("table1"));
XLSX.utils.book_append_sheet(workbook, sheet1, "Sheet1");

/* convert table "table2" to worksheet named "Sheet2" */
var sheet2 = XLSX.utils.table_to_sheet(document.getElementById("table2"));
XLSX.utils.book_append_sheet(workbook, sheet2, "Sheet2");

/* workbook now has 2 worksheets */
```

Alternatively, the HTML code can be extracted and parsed:

```js
var htmlstr = document.getElementById("tableau").outerHTML;
var workbook = XLSX.read(htmlstr, {type:"string"});
```

</details>

<details>
  <summary><b>Chrome/Chromium Extension</b> (click to show)</summary>

The [`chrome` demo](demos/chrome/) shows a complete example and details the
required permissions and other settings.

In an extension, it is recommended to generate the workbook in a content script
and pass the object back to the extension:

```js
/* in the worker script */
chrome.runtime.onMessage.addListener(function(msg, sender, cb) {
  /* pass a message like { sheetjs: true } from the extension to scrape */
  if(!msg || !msg.sheetjs) return;
  /* create a new workbook */
  var workbook = XLSX.utils.book_new();
  /* loop through each table element */
  var tables = document.getElementsByTagName("table")
  for(var i = 0; i < tables.length; ++i) {
    var worksheet = XLSX.utils.table_to_sheet(tables[i]);
    XLSX.utils.book_append_sheet(workbook, worksheet, "Table" + i);
  }
  /* pass back to the extension */
  return cb(workbook);
});
```

</details>

<details>
  <summary><b>Server-Side HTML Tables with Headless Chrome</b> (click to show)</summary>

The [`headless` demo](demos/headless/) includes a complete demo to convert HTML
files to XLSB workbooks.  The core idea is to add the script to the page, parse
the table in the page context, generate a `base64` workbook and send it back
for further processing:

```js
const XLSX = require("xlsx");
const { readFileSync } = require("fs"), puppeteer = require("puppeteer");

const url = `https://sheetjs.com/demos/table`;

/* get the standalone build source (node_modules/xlsx/dist/xlsx.full.min.js) */
const lib = readFileSync(require.resolve("xlsx/dist/xlsx.full.min.js"), "utf8");

(async() => {
  /* start browser and go to web page */
  const browser = await puppeteer.launch();
  const page = await browser.newPage();
  await page.goto(url, {waitUntil: "networkidle2"});

  /* inject library */
  await page.addScriptTag({content: lib});

  /* this function `s5s` will be called by the script below, receiving the Base64-encoded file */
  await page.exposeFunction("s5s", async(b64) => {
    const workbook = XLSX.read(b64, {type: "base64" });

    /* DO SOMETHING WITH workbook HERE */
  });

  /* generate XLSB file in webpage context and send back result */
  await page.addScriptTag({content: `
    /* call table_to_book on first table */
    var workbook = XLSX.utils.table_to_book(document.querySelector("TABLE"));

    /* generate XLSX file */
    var b64 = XLSX.write(workbook, {type: "base64", bookType: "xlsb"});

    /* call "s5s" hook exposed from the node process */
    window.s5s(b64);
  `});

  /* cleanup */
  await browser.close();
})();
```

</details>

<details>
  <summary><b>Server-Side HTML Tables with Headless WebKit</b> (click to show)</summary>

The [`headless` demo](demos/headless/) includes a complete demo to convert HTML
files to XLSB workbooks using [PhantomJS](https://phantomjs.org/). The core idea
is to add the script to the page, parse the table in the page context, generate
a `binary` workbook and send it back for further processing:

```js
var XLSX = require('xlsx');
var page = require('webpage').create();

/* this code will be run in the page */
var code = [ "function(){",
  /* call table_to_book on first table */
  "var wb = XLSX.utils.table_to_book(document.body.getElementsByTagName('table')[0]);",

  /* generate XLSB file and return binary string */
  "return XLSX.write(wb, {type: 'binary', bookType: 'xlsb'});",
"}" ].join("");

page.open('https://sheetjs.com/demos/table', function() {
  /* Load the browser script from the UNPKG CDN */
  page.includeJs("https://unpkg.com/xlsx/dist/xlsx.full.min.js", function() {
    /* The code will return an XLSB file encoded as binary string */
    var bin = page.evaluateJavaScript(code);

    var workbook = XLSX.read(bin, {type: "binary"});
    /* DO SOMETHING WITH workbook HERE */

    phantom.exit();
  });
});
```

</details>

<details>
  <summary><b>NodeJS HTML Tables without a browser</b> (click to show)</summary>

NodeJS does not include a DOM implementation and Puppeteer requires a hefty
Chromium build.  [`jsdom`](https://npm.im/jsdom) is a lightweight alternative:

```js
const XLSX = require("xlsx");
const { readFileSync } = require("fs");
const { JSDOM } = require("jsdom");

/* obtain HTML string.  This example reads from test.html */
const html_str = fs.readFileSync("test.html", "utf8");
/* get first TABLE element */
const doc = new JSDOM(html_str).window.document.querySelector("table");
/* generate workbook */
const workbook = XLSX.utils.table_to_book(doc);
```

</details>