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Creating XLSX Documents in Javascript (Advanced)

In this post we’ll look at how to create XLSX documents in JavaScript with more advanced features such as custom styling and formulas using the xlsx & js-xlsx packages. This works in both NodeJS and React.

  1. What we are Making
  2. Installing Requirements
  3. Data Types
  4. Styling
  5. Formulas

What we are Making

  • If you only need to write text to your XLSX document and don’t require any styling, then the basic version of this guide may be quicker and more suitable.


Installing Requirements

Install the xlsx & js-xlsx packages using the following command:

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npm i xlsx js-xlsx


Data Types

Each sheet in the document will be represented by an Object. The keys of this Object will be the name of the cells (A1, A2, B2, etc).

Each cell in our output document will be represented by another Object. This object will contain information such as the value of the cell, styling, and the output format (number, date, percentage, etc).

More information about supported data types can be found on the XLSX package documentation page here.

Time for examples!

String

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// import XLSX from 'xlsx'; // Use this for React
const XLSX = require('xlsx');
const JS_XLSX = require('js-xlsx');

// Create a new blank XLSX Document
let workbook = XLSX.utils.book_new();

// The data that will be added to the sheet
let worksheetData = {
	'!ref': 'A1:A1', // Sheet Range (Which cells will be included in the output)
	'A1': {
		t: 's', // Type
		v: 'Test String!', // Value
	},
};

// Add the sheet to the workbook
XLSX.utils.book_append_sheet(workbook, worksheetData, 'Sheet 1');

// Save the XLSX File
JS_XLSX.writeFile(workbook, 'FILE_NAME.xlsx');

  • The !ref must contain the output range of the sheet. Cells that are not in this range will not be rendered.
  • The t key in the A1 Object stands for Type. The value of 's' stands for String/Text.
  • The v key in the A1 Object stands for Value. The value here is the text we want in the cell.

Date

To insert a Date, we use the a value of 'd' in the Type field:

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let worksheetData = {
	'!ref': 'A1:B1',
	'A1': { t: 's', v: 'Test String!' },
	'B1': {
		t: 'd',	// Type
		v: (new Date()) // Value
	}
};

Number

When working with numbers we need to specify the number format. We do this by adding another key s which stands for Style/Theme. An Object must be provided as the value and contain a key called numFmt which specifies the number format (Integer, Float, Percentage, Fraction, etc).

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let worksheetData = {
	'!ref': 'A1:C2',
	'A1': {
		t:'n', // Type
		v: 256, // Value
		s: { numFmt: 1 } // Style
	},
	'B1': {
		t:'n',
		v: 3.14159,
		s: { numFmt: 2 }
	},
	'C1': {
		t:'n',
		v: 0.47836,
		s: { numFmt: 10 }
	},
	'A2': {
		t:'n',
		v: 0.47836,
		s: { numFmt: 11 }
	},
	'B2': {
		t:'n',
		v: 0.47836,
		s: { numFmt: 12 }
	},
	'C2': {
		t:'n',
		v: 21567.489,
		s: { numFmt: '_-"$"* #,##0.00_-;\\-"$"* #,##0.00_-;_-"$"* "-"??_-;[email protected]_-' },
	},
};

  • numFmt: 1 means Integer (1, 2, 3 , etc).
  • numFmt: 2 means Float (0.523, 11.25, etc).
  • numFmt: 10 means Percentage (0.85%, 59.23%, etc).
  • numFmt: 11 means Scientific Notation (3.94E+03, 6.85E-01, etc).
  • numFmt: 12 means Single Digit Fraction (1/3, 6/7, etc).
  • numFmt: '_-"$"* #,##0.00_-;\\-"$"* #,##0.00_-;_-"$"* "-"??_-;[email protected]_-' mean Accounting mode ($23,582.64, $0.32, etc).
  • A more complete list of these codes can be found here.


Styling

We can modify the styling by supplying additional parameters to the Object in the s field.

Documentation with additional options can be found here.

Font

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let worksheetData = {
	'!ref': 'A1:B1',
	'A1': {
		t: 's',
		v: 'String 1',
		s: {
			font: {
				name: 'Verdana',
				sz: 20,
				bold: true,
				underline: true,
				italic: true,
				color: { rgb: 'FF12A304' },	// Hex Value: ARGB
			}
		}
	},
	'B1': {
		t: 's',
		v: 'String 2',
		s: {
			font: {
				name: 'Times New Roman',
				sz: 10,
				strike: true,
			}
		}
	},
};

Alignment

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let worksheetData = {
	'!ref': 'A1:B1',
	'A1': {
		t: 's',
		v: 'String 1',
		s: {
			font: {
				name: 'Verdana',
			},
			alignment: {
				horizontal: 'left',
				vertical: 'bottom',
			}
		}
	},
	'B1': {
		t: 's',
		v: 'String 2',
		s: {
			font: {
				name: 'Arial',
			},
			alignment: {
				horizontal: 'right',
				vertical: 'top',
			}
		}
	},
};

Fill

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let worksheetData = {
	'!ref': 'A1:B1',
	'A1': {
		t:'s',
		v: 'COLOURS!',
		s: {
			font: {
				name: 'IMPACT',
				sz: 32,
				color: { rgb: 'FFE609EA' },	// ARGB Hex Value
			},
			fill: {
				fgColor: { rgb: 'FF0269D8' },	// ARGB Hex Value
			},
			alignment: {
				horizontal: 'center',
				vertical: 'center',
			}
		}
	},
};


Formulas

At the time of writing the js-xlsx module doesn’t yet support formulas. This is inconvenient because the xlsx module does support formulas, but it doesn’t support styling. We don’t want to choose between styling and formulas, we want both.

Luckily, there are smart people who’ve had the same issue and made a fix!

How do I Make it Work?

For reference the package versions being used in this guide are:

  • js-xlsx: 0.8.22
  • xlsx: 0.16.9

From the above screenshot we can add formula support into js-xlsx with 2 small code changes:

  1. Open the file node_modules/js-xlsx/xlsx.js.
  2. Replace line 7685 with the following line:
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    if ( ! (cell.v || cell.s ||  cell.f ) ) return "";
    
  3. Replace line 7710 with the following 2 lines:
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    var o = { r: ref };
    var v = cell.f ? writetag('f', escapexml(cell.f)) : writetag('v', escapexml(vv));
    
  4. Done!!!

Formula Example

To add a formula we need to create an f key in our cell Object and store our formula there:

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let worksheetData = {
	'!ref': 'A1:E2',

	// Generate some random values in the second row 
	'A2': { t: 'n', v: Math.round(Math.random()*100), s: { numFmt: 1 } },
	'B2': { t: 'n', v: Math.round(Math.random()*100), s: { numFmt: 1 } },
	'C2': { t: 'n', v: Math.round(Math.random()*100), s: { numFmt: 1 } },
	'D2': { t: 'n', v: Math.round(Math.random()*100), s: { numFmt: 1 } },

	// Add a header
	'E1': { t: 's', v: 'Total Sum', s: { font: { bold: true, underline: true } } },
	
	// Add formula
	'E2': {
		t: 'n',
		f: 'SUM(A2:D2)'
	},
};

This post is licensed under CC BY 4.0 by the author.