processing-excel-fileslisted

# Processing Excel Files Edit and manipulate Excel files using the xlsx-populate library while perfectly preserving original formatting. ## When to Use - User wants to edit existing Excel files without destroying formatting - Working with .xlsx files that have complex layouts or merged cells - Need to add formulas, styling, or new worksheets to existing files - Creating Excel reports from templates ## When NOT to Use - Only need to read data from Excel (use `xlsx` library instead for better performance) - Creating simple Excel files from scratch without formatting concerns ## Quick Start ```javascript const XlsxPopulate = require('xlsx-populate'); // Load and edit const workbook = await XlsxPopulate.fromFileAsync('input.xlsx'); workbook.sheet(0).cell('A1').value('Updated'); await workbook.toFileAsync('output.xlsx'); ``` ## Installation ```bash npm install xlsx-populate ``` ## Core Operations ### 1. Load and Preserve Formatting ```javascript const workbook = await XlsxPopulate.fromFileAsync('file.xlsx'); const sheet = workbook.sheet(0); // All original formatting is preserved automatically sheet.cell('A1').value('New Value'); await workbook.toFileAsync('output.xlsx'); ``` ### 2. Add Formulas ```javascript // Use formulas, not hardcoded values sheet.cell('D10').formula('=SUM(D2:D9)'); sheet.cell('E5').formula('=(C5-B5)/B5'); // Growth rate ``` ### 3. Apply Styles ```javascript sheet.cell('A1').style({ bold: true, fontSize: 14, fill: '4472C4', fontColo