Edit and create Excel (.xlsx) files while preserving original formatting, merged cells, and styles. Use when working with Excel files, spreadsheets, .xlsx files, or when the user mentions editing Excel without destroying formatting.

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 Installation Core Operations 1. Load and Preserve Formatting 2. Add Formulas 3. Apply Styles 4. Manage Worksheets 5. Merge Cells Advanced Patterns Batch Data Writing : See [BATCH OPERATIONS.md] for large dataset handling Formula Patterns : See [FORMULAS.md] for financial modeling standards Style Guide : See [STYLES.md] for color schemes and formatting Complete Examples : See [EXAMPLES.md] for real world scenarios Best Practices 1. Always preserve originals : Never overwrite source files 2. Use formulas for calculations : Let Excel do the math 3. Handle errors gracefully : Common Issues Q: File size increased significantly? A: Normal xlsx populate preserves more metadata. Use xlsx library if file size is critical. Q: Formulas not calculating? A: Formulas are preserved but calculated when opened in Excel. Use data only=True to read calculated values. Q: How to check merged cells? A: const merges = sheet. mergeCells; Reference [xlsx populate GitHub](https://github.com/dtjohnson/xlsx populate) Library documentation: node modules/xlsx populate/docs/

processing-excel-files