TLDR: An Open Source fork of SheetJS lets you create and style Excel spreadsheets with JavaScript.

Creating XLSX Files

An XLSX file is a Microsoft Excel spreadsheet.

I previously documented How to Download xlsx Files from a Next.js Route Handler.

In that blog post, I used the xlsx package which is also known as SheetJS.

However, I discovered a limitation of the community edition of the xlsx package: It did not allow the row and cell styling that my stakeholders desired in their final product.

The PRO edition does allow styling, but I looked for an open source solution and found it.

xlsx-js-style

xlsx-js-style is a fork of SheetJS combined with code from a couple of other open source projects that were adding styles to SheetJS.

The only drawback I see is the last version was published 2 years ago, but it does not have the vulnerability I warned about if you install the xlsx dependency directly from npm.

xlsx-js-style allows you to create Excel spreadsheets with JavaScript and style the cells with borders, colors, alignment, and font styles.

Add xlsx-js-style to Your Project

Install xlsx:

npm i xlsx-js-style

Next, import xlsx-js-style into your project:

import XLSX from "xlsx-js-style"

You can use this package in any JavaScript or TypeScript project.

Creating and Styling the XLSX Worksheet

Here's an example of how to use the xlsx-js-style package:

// define your headers 
const headers = [
    "FirstName",
    "LastName",
    "Email",
]

// set column widths
const colWidths = [
        { wch: 30 },
        { wch: 30 },
        { wch: 50 },
]

// get the data 
const userData = await getUserData()

// early return if no data
if (!userData || !userData[0]) {
    return null
}

// set header row height 
// consider if you have vertical headers
const headerRowHeight = [
    { hpt: 80 },
]

// Dynamically set row height based on size of data
const dataRowHeight = Array.from({ length: userData[0].length }, () => ({ hpt: 30 }))

// Combine header row height and data row height
const rowHeight = [...headerRowHeight, ...dataRowHeight]

// Create a new worksheet: 
const worksheet = XLSX.utils.json_to_sheet([])

// Assign widths to columns
worksheet['!cols'] = colWidths

// Assign height to rows
worksheet['!rows'] = rowHeight

// Enable auto-filter for columns
worksheet['!autofilter'] = { ref: "A1:C1" }

// Add the headers to the worksheet: 
XLSX.utils.sheet_add_aoa(worksheet, [headers])

// add data to sheet 
XLSX.utils.sheet_add_json(worksheet, userData, {
    skipHeader: true,
    origin: -1
})

// get size of sheet 
const range = XLSX.utils.decode_range(worksheet["!ref"] ?? "")
const rowCount = range.e.r
const columnCount = range.e.c

// Add formatting by looping through data in sheet 
for (let row = 0; row <= rowCount; row++) {
    for (let col = 0; col <= columnCount; col++) {
        const cellRef = XLSX.utils.encode_cell({ r: row, c: col })

        // Add this format to every cell
        worksheet[cellRef].s = {
            alignment: {
                horizontal: "left",
                wrapText: true,
            },
        }

        // vertical header - 1st column only
        if (row === 0 && col === 0) {
            worksheet[cellRef].s = {
                //spreads in previous cell settings
                ...worksheet[cellRef].s,
                alignment: {
                    horizontal: "center",
                    vertical: "center",
                    wrapText: false,
                    textRotation: 180,
                },
            }
        }

        // Format headers bold
        if (row === 0) {
            worksheet[cellRef].s = {
                //spreads in previous cell settings
                ...worksheet[cellRef].s, 
                font: { bold: true },
            }
        }

    }
}

return worksheet

// After this, add worksheet to workbook, download, etc. 
// See docs and my previous article

Other Styles Available

I only applied a few of the styles available in the above example.

Checkout all of the available style settings on the npm page for xlsx-js-style.

Learning More:

Read my previous article on How to Download xlsx Files if you want to create these files in a Node.js backend and request them from your frontend. My example is with Next.js, but you could just set it up in Node.js without Next.js.
If you read the previous article or watch the video below, remember to replace the xlsx dependency with the xlsx-js-style dependency I discussed in this article.

Enjoy creating Excel spreadsheets with JavaScript!