--- title: Excel JavaScript API pagination_prev: demos/cloud/index pagination_next: demos/bigdata/index --- import current from '/version.js'; :::info This demo focuses on the JavaScript API included with Excel. For reading and writing Excel files, [other demos](/docs/demos/) cover a wide variety of use cases ::: Office 2016 introduced a JavaScript API for interacting with the application. It offers solutions for custom functions as well as task panes. Excel currently does not provide support for working with Apple Numbers files and some legacy file formats. SheetJS fills the gap. This demo creates a new custom function `SHEETJS.EXTERN()` which tries to fetch an external spreadsheet and insert the data into the worksheet. ![`SHEETJS.EXTERN` output](pathname:///xlapi/xlfetch.png) This demo focuses on the basic mechanics. Advanced topics like Excel Custom Function parameters are covered in the official Office JavaScript API docs. :::note This demo was last tested on 2023 April 20 against Excel 365 (version 2303) ::: :::caution Excel Bugs There was a binary data bug affecting `fetch` and Excel. It was resolved in version 2303. It is strongly encouraged to upgrade to the latest version of Excel 365 before running the demo. ::: ## Integration Details The [NodeJS module](/docs/getting-started/installation/nodejs) can be imported in an Excel Custom Functions project. The [`sheet_to_json`](/docs/api/utilities#json) helper function can generate arrays of arrays of values based on the worksheet data. Excel custom functions transparently treat these as Dynamic Arrays. This example fetches a file, parses the data, and extracts the first worksheet: ```js title="src\functions\functions.js" var XLSX = require("xlsx"); /** * Download file and write data * @customfunction * @param {string} url URL to fetch and parse * @returns {any[][]} Worksheet data */ async function extern(url) { try { /* Fetch Data */ const res = await fetch(url); /* Get Data */ const ab = await res.arrayBuffer(); /* Parse Data */ var wb = XLSX.read(ab); /* get and return data */ var ws = wb.Sheets[wb.SheetNames[0]]; // get first worksheet var aoa = XLSX.utils.sheet_to_json(ws, { header: 1 }); // array of arrays return aoa; } catch(e) { return [[e.message || e]]; } // pass error back to Excel } ``` ## Complete Demo 0) Clear the functions cache. For the tested version of Excel: - Open File Explorer - Select the address bar and enter `%LOCALAPPDATA%\Microsoft\Office\16.0\Wef` - Delete `CustomFunctions` and empty Recycle Bin. 1) Install [NodeJS LTS](https://nodejs.org/en/download/). 2) Install dependencies in a new PowerShell window: ```powershell npm install -g yo bower generator-office ``` ### Creating a new Add-in 3) Run `yo office` from the command line. It will ask a few questions: - "Choose a project type": "Excel Custom Functions using a Shared Runtime" - "Choose a script type": "JavaScript", - "What do you want to name your add-in?": "SheetJSImport" 4) Start the dev process: ```powershell cd SheetJSImport npm run build npm start ``` Running `npm start` will open up a terminal window and a new Excel window with the loaded add-in. Keep the terminal window open. 5) In `manifest.xml` , search for `Functions.NameSpace` . There will be an XML element with name `bt:String`. Change the `DefaultValue` attribute to `SHEETJS`: ```xml title="manifest.xml" // highlight-next-line ``` 6) Close the Excel window and the terminal window, then run `npm start` again. ### Integrating the SheetJS Library 7) Install the SheetJS library in the project
{`\
npm i --save https://cdn.sheetjs.com/xlsx-${current}/xlsx-${current}.tgz`}
8) Replace `src\functions\functions.js` with the following: ```js title="src\functions\functions.js" var XLSX = require("xlsx"); /** * Print SheetJS Library Version * @customfunction * @returns {string[][]} The SheetJS Library Version. */ function version() { return [[XLSX.version]]; } ``` 9) After making the change, save the files. Close the terminal window and the Excel window (do not save the Excel file). Re-run `npm start`. 10) In the new Excel window, enter the formula `=SHEETJS.VERSION()` in cell `E1`. You should see something similar to the following screenshot: ![`SHEETJS.VERSION` output](pathname:///xlapi/xlvers.png) This indicates that the SheetJS library has been loaded. ### Fetching Files from the Internet 11) Add the following code snippet to `src\functions\functions.js`: ```js src\functions\functions.js /** * Download file and write data * @customfunction * @param {string} url URL to fetch and parse * @returns {any[][]} Worksheet data */ async function extern(url) { try { /* Fetch Data */ const res = await fetch(url); /* Get Data */ const ab = await res.arrayBuffer(); /* Parse Data */ var wb = XLSX.read(ab); /* get and return data */ var ws = wb.Sheets[wb.SheetNames[0]]; // get first worksheet var aoa = XLSX.utils.sheet_to_json(ws, { header: 1 }); // get data as array of arrays return aoa; } catch(e) { return [[e.message || e]]; } // pass error back to Excel } ``` 12) After making the change, save the files. Close the terminal window and the Excel window (do not save the Excel file). Re-run `npm start`. 13) Enter the text `https://sheetjs.com/pres.numbers` in cell `D1`. Enter the formula `=SHEETJS.EXTERN(D1)` in cell `D2` and press Enter. Excel should pull in the data and generate a dynamic array. :::note [SheetJS Pro](https://sheetjs.com/pro) offers additional features that can be used in Excel Custom Functions and Add-ins :::