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

1. Template Mode: Modify existing branded templates

   • Analyze template to find placeholders and structure
   • Replace {{PLACEHOLDERS}} with actual values

2. 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

Specification Reference

Sheet Options

Cell Options

Column Options

Template Replacement Options

Common Issues and Solutions

Issue: Placeholders not being replaced

Symptoms: Output XLSX still contains {{PLACEHOLDER}} tags.

Solution:

1. Run analyze-template.ts to verify exact tag text and location
2. Check that placeholder is in a string cell, not a formula
3. 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)

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