XLSX Generator When to Use This Skill
Use this skill when:
Creating Excel spreadsheets programmatically from data or specifications Populating branded templates with dynamic content while preserving formatting Extracting cell data, formulas, and structure from existing XLSX files Finding and replacing placeholder text like {{TITLE}} or ${date} in cells Automating spreadsheet generation workflows (reports, data exports, financial statements)
Do NOT use this skill when:
User wants to open/view spreadsheets (use native Excel or viewer) Complex pivot tables or charts are required (limited support) Working with older .xls format (XLSX only) Real-time collaborative editing is needed Prerequisites Deno installed (https://deno.land/) Input XLSX files for template-based operations JSON specification for scratch generation Quick Start Two Modes of Operation
Template Mode: Modify existing branded templates
Analyze template to find placeholders and structure Replace {{PLACEHOLDERS}} with actual values
Scratch Mode: Create spreadsheets from nothing using JSON specifications
Instructions Mode 1: Template-Based Generation Step 1a: Analyze the Template
Extract cell inventory to understand what can be replaced:
deno run --allow-read scripts/analyze-template.ts financial-template.xlsx > inventory.json
Output (inventory.json):
{ "filename": "financial-template.xlsx", "sheetCount": 3, "sheets": [ { "name": "Summary", "rowCount": 25, "colCount": 8, "usedRange": "A1:H25", "cells": [ { "address": "A1", "row": 1, "col": 1, "value": "{{REPORT_TITLE}}", "type": "string" }, { "address": "B3", "row": 3, "col": 2, "value": "{{DATE}}", "type": "string" }, { "address": "C5", "row": 5, "col": 3, "value": null, "type": "number", "formula": "SUM(C6:C20)" } ] } ], "placeholders": [ { "tag": "{{REPORT_TITLE}}", "location": "Summary!A1", "sheet": "Summary", "address": "A1" }, { "tag": "{{DATE}}", "location": "Summary!B3", "sheet": "Summary", "address": "B3" } ], "hasFormulas": true }
Step 1b: Create Replacement Specification
Create replacements.json:
{ "textReplacements": [ { "tag": "{{REPORT_TITLE}}", "value": "Q4 2024 Financial Report" }, { "tag": "{{DATE}}", "value": "December 15, 2024" }, { "tag": "{{COMPANY}}", "value": "Acme Corporation", "sheets": ["Summary", "Cover"] } ], "cellUpdates": [ { "sheet": "Data", "address": "B5", "value": 1250000 }, { "sheet": "Data", "address": "B6", "value": 750000 } ] }
Step 1c: Generate Output deno run --allow-read --allow-write scripts/generate-from-template.ts \ financial-template.xlsx replacements.json output.xlsx
Mode 2: From-Scratch Generation Step 2a: Create Specification
Create spec.json:
{ "title": "Sales Report", "author": "Finance Team", "sheets": [ { "name": "Sales Data", "data": [ ["Product", "Q1", "Q2", "Q3", "Q4", "Total"], ["Widget A", 10000, 12000, 15000, 18000, null], ["Widget B", 8000, 9000, 11000, 13000, null], ["Widget C", 5000, 6000, 7000, 8000, null] ], "cells": [ { "address": "F2", "formula": "SUM(B2:E2)" }, { "address": "F3", "formula": "SUM(B3:E3)" }, { "address": "F4", "formula": "SUM(B4:E4)" } ], "columns": [ { "col": "A", "width": 15 }, { "col": "B", "width": 10 }, { "col": "C", "width": 10 }, { "col": "D", "width": 10 }, { "col": "E", "width": 10 }, { "col": "F", "width": 12 } ], "freezePane": "A2", "autoFilter": "A1:F4" } ] }
Step 2b: Generate Spreadsheet deno run --allow-read --allow-write scripts/generate-scratch.ts spec.json output.xlsx
Examples Example 1: Monthly Sales Report
Scenario: Generate a monthly sales report from template.
Steps:
1. Analyze template for replaceable content
deno run --allow-read scripts/analyze-template.ts sales-template.xlsx --pretty
2. Create replacements.json with monthly data
3. Generate report
deno run --allow-read --allow-write scripts/generate-from-template.ts \ sales-template.xlsx replacements.json November-Sales.xlsx
Example 2: Data Export with Formulas
Scenario: Create a spreadsheet with calculated totals.
spec.json:
{ "sheets": [{ "name": "Expenses", "data": [ ["Category", "January", "February", "March", "Total"], ["Office", 1500, 1600, 1400, null], ["Travel", 3000, 2500, 4000, null], ["Software", 500, 500, 500, null], ["Total", null, null, null, null] ], "cells": [ { "address": "E2", "formula": "SUM(B2:D2)" }, { "address": "E3", "formula": "SUM(B3:D3)" }, { "address": "E4", "formula": "SUM(B4:D4)" }, { "address": "B5", "formula": "SUM(B2:B4)" }, { "address": "C5", "formula": "SUM(C2:C4)" }, { "address": "D5", "formula": "SUM(D2:D4)" }, { "address": "E5", "formula": "SUM(E2:E4)" } ] }] }
Example 3: Multi-Sheet Workbook
Scenario: Create a workbook with summary and detail sheets.
spec.json:
{ "title": "Q4 Report", "sheets": [ { "name": "Summary", "data": [ ["Department", "Budget", "Actual", "Variance"], ["Sales", 500000, 520000, null], ["Marketing", 200000, 195000, null] ], "cells": [ { "address": "D2", "formula": "C2-B2" }, { "address": "D3", "formula": "C3-B3" } ] }, { "name": "Sales Detail", "data": [ ["Month", "Revenue", "Cost", "Profit"], ["October", 180000, 120000, null], ["November", 170000, 115000, null], ["December", 170000, 110000, null] ], "cells": [ { "address": "D2", "formula": "B2-C2" }, { "address": "D3", "formula": "B3-C3" }, { "address": "D4", "formula": "B4-C4" } ] } ] }
Script Reference Script Purpose Permissions analyze-template.ts Extract cells, formulas, placeholders from XLSX --allow-read generate-from-template.ts Replace placeholders in templates --allow-read --allow-write generate-scratch.ts Create XLSX from JSON specification --allow-read --allow-write Specification Reference Sheet Options Property Type Description name string Sheet name data array 2D array of cell values starting at A1 cells array Individual cell specifications rows array Row-based data specifications columns array Column width and visibility settings merges array Merged cell ranges freezePane string Freeze panes at this cell (e.g., "A2") autoFilter string Auto-filter range (e.g., "A1:F10") Cell Options Property Type Description address string Cell address (e.g., "A1", "B2") value mixed Cell value (string, number, boolean, null) formula string Formula without = sign format string Number format (e.g., "#,##0.00") type string Force type: "string", "number", "boolean", "date" Column Options Property Type Description col string Column letter (e.g., "A", "B", "AA") width number Column width in characters hidden boolean Hide column Template Replacement Options Property Type Description tag string Placeholder to find (e.g., "{{TITLE}}") value mixed Replacement value sheets array Limit to specific sheets range string Limit to cell range (e.g., "A1:D10") Common Issues and Solutions Issue: Placeholders not being replaced
Symptoms: Output XLSX still contains {{PLACEHOLDER}} tags.
Solution:
Run analyze-template.ts to verify exact tag text and location Check that placeholder is in a string cell, not a formula Verify sheet filter in replacement spec Issue: Formulas showing as text
Symptoms: Formulas display as text instead of calculating.
Solution:
Ensure formula doesn't start with "=" in spec (it's added automatically) Check cell type is not forced to "string" Issue: Numbers formatted as text
Symptoms: Numbers have green triangle indicating text storage.
Solution:
Use numeric values in spec, not quoted strings For template replacement, if entire cell is placeholder and replacement is number, it converts automatically Issue: Column widths not applied
Symptoms: Columns have default width despite specification.
Solution:
Ensure column letters are uppercase Verify column spec is in array format Limitations XLSX only: Does not support legacy .xls or .xlsb formats No macros: Cannot create or preserve VBA macros Limited charting: No native chart creation support No pivot tables: Cannot create pivot tables programmatically Basic styling: Limited cell formatting options No conditional formatting: Cannot set conditional format rules Formula recalc: Formulas are stored but not recalculated (Excel recalculates on open) Related Skills pptx-generator: For creating PowerPoint presentations docx-generator: For creating Word documents csv-processor: For simpler CSV data processing