exceljs

A Node.js library for reading, editing, and writing Excel XLSX spreadsheet files, including formatting, formulas, charts, and large-file streaming.

In plain words
What is it for?
Creating reports, changing spreadsheet data and styles, calculating values with formulas, adding charts, and processing large workbooks.
Why use it?
It lets software generate or update Excel workbooks without requiring someone to edit them manually.

Skill for Claude CodeCodex

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add skills/aidotnet/moyucode/exceljs
Any agent
npx skills add AIDotNet/MoYuCode --skill exceljs
Clone the repo
git clone --depth 1 https://github.com/AIDotNet/MoYuCode

Made for: Claude Code, Codex.

Per session 38 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,082 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00038 $0.01082
Opus 5 $0.00019 $0.00541
Sonnet 5 $0.00008 $0.00216
Haiku 4.5 $0.00004 $0.00108

Measured 3d ago against content hash 3009892b2e22, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

exceljs scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 3d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

skills/tools/exceljs/SKILL.md · 167 lines

How it starts

The opening of the file, as written. The whole thing — 167 lines — stays where its author put it; the contents beside it link to each section on GitHub.

ExcelJS Tool

Description

Read, manipulate, and write Excel spreadsheets with full formatting support.

Source

Installation

npm install exceljs

Usage Examples

Create Excel File

import ExcelJS from 'exceljs';

async function createReport() {
  const workbook = new ExcelJS.Workbook();
  workbook.creator = 'My App';
  workbook.created = new Date();
  
  const sheet = workbook.addWorksheet('Sales Report');
  
  // Define columns
  sheet.columns = [
    { header: 'ID', key: 'id', width: 10 },
    { header: 'Product', key: 'product', width: 30 },
    { header: 'Quantity', key: 'quantity', width: 15 },
    { header: 'Price', key: 'price', width: 15 },
    { header: 'Total', key: 'total', width: 15 },
  ];
  
  // Add data
  const data = [
    { id: 1, product: 'Widget A', quantity: 100, price: 9.99 },
    { id: 2, product: 'Widget B', quantity: 50, price: 19.99 },
    { id: 3, product: 'Widget C', quantity: 75, price: 14.99 },
  ];
  
  data.forEach(item => {
    sheet.addRow({
      ...item,
      total: { formula: `C${sheet.rowCount + 1}*D${sheet.rowCount + 1}` },
    });
  });
  
  await workbook.xlsx.writeFile('report.xlsx');
}

Style Cells

async function createStyledReport() {
  const workbook = new ExcelJS.Workbook();
  const sheet = workbook.addWorksheet('Styled');
  
  // Header row with styling
  const headerRow = sheet.addRow(['Name', 'Email', 'Status']);
  headerRow.eachCell(cell => {
    cell.fill = {
      type: 'pattern',
      pattern: 'solid',
      fgColor: { argb: '4F46E5' },
    };
    cell.font = { color: { argb: 'FFFFFF' }, bold: true };
    cell.alignment = { horizontal: 'center' };
    cell.border = {
      top: { style: 'thin' },
      bottom: { style: 'thin' },
    };
  });
  
  // Data rows
  const users = [
    { name: 'John', email: '[email protected]', status: 'Active' },
    { name: 'Jane', email: '[email protected]', status: 'Inactive' },
  ];
  
  users.forEach(user => {
    const row = sheet.addRow([user.name, user.email, user.status]);
    
    // Conditional formatting
    const statusCell = row.getCell(3);
    statusCell.fill = {
      type: 'pattern',
      pattern: 'solid',
      fgColor: { argb: user.status === 'Active' ? '22C55E' : 'EF4444' },
    };
  });
  
  await workbook.xlsx.writeFile('styled-report.xlsx');
}

Read the full file on GitHub · 167 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 3d ago First seen · 167 lines · 38 tokens per session scan A 3009892b2e22

Subscribe to this mod's changes

exceljs is a skill published in the GitHub repository AIDotNet/MoYuCode (84 stars, last pushed 7mo ago), licensed MIT. It adds 38 tokens to every session and 1,082 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

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