headless-spreadjs

Headless Excel engine for Node.js using SpreadJS. Runs without a browser or Excel.

Features

• Read/write .xlsx and .xlsm
• High-fidelity formulas, styles, tables, charts, pivots
• SpreadJS JSON roundtrip (toJSON / fromJSON)
• CLI (hsx) for quick workbook ops

System dependencies

canvas requires Cairo/Pango.

# macOS
brew install pkg-config cairo pango libpng jpeg giflib librsvg

# Debian/Ubuntu
sudo apt-get install build-essential libcairo2-dev libpango1.0-dev libjpeg-dev libgif-dev librsvg2-dev

Install

npm install @hewliyang/headless-spreadjs

SDK quick start

import { init } from "@hewliyang/headless-spreadjs";

const { ExcelFile, dispose } = await init({ licenseKey: "xxx" });

const file = new ExcelFile();
const sheet = file.workbook.getActiveSheet();
sheet.setValue(0, 0, "Name");
sheet.setValue(0, 1, "Score");
sheet.setValue(1, 0, "Alice");
sheet.setValue(1, 1, 95);
await file.save("output.xlsx");

dispose();

CLI quick start

hsx create scores.xlsx
hsx set scores.xlsx A1:B3 '[["Name","Score"],["Alice",95],["Bob",87]]'
hsx get scores.xlsx A1:B3
hsx csv scores.xlsx A1:B3
hsx search scores.xlsx "Alice"
hsx diff before.xlsx after.xlsx
hsx deps scores.xlsx Sheet1!A1

Run hsx --help for all commands.

Daemon (CLI)

hsx uses a background daemon by default to avoid re-initializing SpreadJS on each command.

• Auto-starts on first use
• Caches open workbooks
• Auto-exits after 5 minutes idle
• Falls back to direct mode if daemon is unavailable

Useful commands:

hsx daemon start
hsx daemon status
hsx daemon flush
hsx daemon stop
hsx --no-daemon get file.xlsx A1
hsx --timeout 120 eval file.xlsx '/* script */'

Environment variables:

Variable	Default	Purpose
HSX_SOCKET_PATH	platform default	Custom daemon socket/pipe
HSX_CACHE_SIZE	10	LRU workbook cache size
HSX_WRITE_THROUGH	0	Immediate writes when truthy

Hooks

hsx supports extension hooks — custom code that runs at specific points in the CLI workflow. Use them to enforce formatting conventions, set workbook defaults, validate before save, etc.

Discovery

Hook files are auto-discovered from:

1. .headless-spreadjs/hooks/*.ts — project-local (takes precedence)
2. ~/.headless-spreadjs/hooks/*.ts — global fallback

TypeScript hooks are transpiled on the fly via jiti.

Hook points

Hook	When	Context
preCommand	Before CLI command dispatch	{ command, args }
onOpen	After workbook opened, before command runs	Full HookContext
preSave	After mutations, before save()	Full HookContext with mutatedRanges
postSave	After save() completes	Full HookContext with mutatedRanges
postCommand	After CLI command completes	{ command, args, error? }

HookContext includes command, args, filePath, file (ExcelFile), workbook (SpreadJS Workbook), GC (SpreadJS namespace), and mutatedRanges.

In daemon mode, onOpen fires on every command (not just the first open), since the workbook stays cached in memory.

Writing a hook

Hook files export a default function that receives a HookAPI instance:

// no-gridlines.ts
import type { HookAPI, HookContext } from "@hewliyang/headless-spreadjs/hooks";

function hideGridlines(ctx: HookContext) {
  for (let i = 0; i < ctx.workbook.getSheetCount(); i++) {
    const sheet = ctx.workbook.getSheet(i);
    sheet.options.gridline = {
      showVerticalGridline: false,
      showHorizontalGridline: false,
    };
  }
}

export default function (hsx: HookAPI) {
  hsx.on("onOpen", hideGridlines);
}

Fine-grained mutations

Commands like set, clear, and copy report exactly which cells they changed via ctx.mutatedRanges. Hooks can use this to only process affected cells instead of scanning the entire workbook:

// color-inputs.ts
import type { HookAPI, HookContext } from "@hewliyang/headless-spreadjs/hooks";

function colorInputs(ctx: HookContext) {
  for (const range of ctx.mutatedRanges) {
    const ws = range.sheet
      ? ctx.workbook.getSheetFromName(range.sheet)
      : ctx.workbook.getActiveSheet();

    for (let r = range.startRow; r <= range.endRow; r++) {
      for (let c = range.startCol; c <= range.endCol; c++) {
        const formula = ws.getFormula(r, c);
        if (!formula && typeof ws.getValue(r, c) === "number") {
          ws.getCell(r, c).foreColor("Blue");
        }
      }
    }
  }
}

export default function (hsx: HookAPI) {
  hsx.on("preSave", colorInputs);
}

For opaque commands like eval, mutatedRanges is empty — hooks can fall back to scanning all used cells.

Output

Hook console.log output is captured and prefixed with [hook-type:fnName]. By default output goes to stderr. Override per-hook:

// custom-output.ts
import type { HookAPI, HookContext } from "@hewliyang/headless-spreadjs/hooks";

function myHook(ctx: HookContext) {
  console.log(`saving ${ctx.filePath}`);
}

function quietHook(ctx: HookContext) {
  /* silent work */
}

export default function (hsx: HookAPI) {
  hsx.on("preSave", { output: "stdout" }, myHook);
  hsx.on("preSave", { output: "none" }, quietHook);
}

Disabling hooks

hsx --no-hooks set file.xlsx A1 '[[{"value":1}]]'

Examples

See examples/hooks/ for ready-to-use hooks:

• financial-colors.ts — auto-colors cells by type (Blue = hardcoded, Black = formula, Green = cross-sheet link) and lints violations after save
• hardcode-lint.ts — flags suspicious numeric literals embedded inside formulas while ignoring common low-noise cases like ROUND(..., 2) and INDEX(..., 1, 2)
• no-gridlines.ts — hides gridlines on all sheets when a workbook is opened

SDK API

init(options?)

Initializes runtime and returns { GC, ExcelFile, dispose }.

• licenseKey?: string — SpreadJS license key (omit for trial)

ExcelFile

• new ExcelFile()
• ExcelFile.open(path)
• ExcelFile.openFromBuffer(buf)
• file.save(path)
• file.saveToBuffer()
• file.toJSON()
• file.fromJSON(json)
• file.batch(fn)
• file.workbook (raw GC.Spread.Sheets.Workbook)

GC

Full SpreadJS namespace (GC.Spread.Sheets.*) for advanced APIs (styles, enums, tables, formatting, etc).

dispose()

Closes the DOM shim runtime. Call when all workbook work is done.

Concurrency notes

A process supports one active init()/dispose() lifecycle at a time. Multiple ExcelFile instances are fine within that lifecycle.

For isolation, use child processes (not worker threads).

Docker

FROM node:20-slim
RUN apt-get update && apt-get install -y \
    build-essential libcairo2-dev libpango1.0-dev \
    libjpeg-dev libgif-dev librsvg2-dev \
    && rm -rf /var/lib/apt/lists/*

License

MIT for this package. SpreadJS requires a separate commercial license from MESCIUS.