sheetjs_sheetjs/docbits/13_usage.md

Usage

Most scenarios involving spreadsheets and data can be broken into 5 parts:

1. Acquire Data: Data may be stored anywhere: local or remote files, databases, HTML TABLE, or even generated programmatically in the web browser.

2. Extract Data: For spreadsheet files, this involves parsing raw bytes to read the cell data. For general JS data, this involves reshaping the data.

3. Process Data: From generating summary statistics to cleaning data records, this step is the heart of the problem.

4. Package Data: This can involve making a new spreadsheet or serializing with JSON.stringify or writing XML or simply flattening data for UI tools.

5. Release Data: Spreadsheet files can be uploaded to a server or written locally. Data can be presented to users in an HTML TABLE or data grid.

A common problem involves generating a valid spreadsheet export from data stored in an HTML table. In this example, an HTML TABLE on the page will be scraped, a row will be added to the bottom with the date of the report, and a new file will be generated and downloaded locally. XLSX.writeFile takes care of packaging the data and attempting a local download:

// Acquire Data (reference to the HTML table)
var table_elt = document.getElementById("my-table-id");

// Extract Data (create a workbook object from the table)
var workbook = XLSX.utils.table_to_book(table_elt);

// Process Data (add a new row)
var worksheet = workbook.Sheets["Sheet1"];
XLSX.utils.sheet_add_aoa([["Created "+new Date().toISOString()}]], {origin:-1});

// Package and Release Data (`writeFile` tries to write and save an XLSB file)
XLSX.writeFile(workbook, "Report.xlsb");

This library tries to simplify steps 2 and 4 with functions to extract useful data from spreadsheet files (read / readFile) and generate new spreadsheet files from data (write / writeFile).

This documentation and various demo projects cover a number of common scenarios and approaches for steps 1 and 5.

Utility functions help with step 3.

The Zen of SheetJS

File formats are implementation details

The parser covers a wide gamut of common spreadsheet file formats to ensure that "HTML-saved-as-XLS" files work as well as actual XLS or XLSX files.

The writer supports a number of common output formats for broad compatibility with the data ecosystem.

Data processing should fit in any workflow

The library does not impose a separate lifecycle. It fits nicely in websites and apps built using any framework. The plain JS data objects play nice with Web Workers and future APIs.

"Parsing Workbooks" describes solutions for common data import scenarios involving actual spreadsheet files.

"Writing Workbooks" describes solutions for common data export scenarios involving actual spreadsheet files.

"Utility Functions" details utility functions for translating JSON Arrays and other common JS structures into worksheet objects.

JavaScript is a powerful language for data processing

The "Common Spreadsheet Format" is a simple object representation of the core concepts of a workbook. The various functions in the library provide low-level tools for working with the object.

For friendly JS processing, there are utility functions for converting parts of a worksheet to/from an Array of Arrays. For example, summing columns from an array of arrays can be implemented in a single Array reduce operation:

var aoa = XLSX.utils.sheet_to_json(worksheet, {header: 1});
var sum_of_column_B = aoa.reduce((acc, row) => acc + (+row[1]||0), 0);