FeHelper - Frontend Helper

---

Feature overview

JSON

Feature	Description
JSON formatter	Auto/manual format, syntax highlighting, fold/unfold, node path, lossless BigInt precision
JSON diff	Structured diff between two JSON documents with highlighted differences
JSON to Excel	One-click export of JSON data to Excel

Encode/Decode

Feature	Description
Unicode	Chinese ↔ \uXXXX conversion
URL / UTF-8 / UTF-16	%XX / \xXX encode and decode
Base64	Encode and decode
Hex	String ↔ hexadecimal
MD5 / SHA1	Digest
Gzip	Compress/decompress via CompressionStream API
JWT	Decode Header + Payload + Sign
Cookie	Format as JSON
HTML entities	Normal/deep encode and decode
String escaping	Escape/unescape \n \t \", etc.

Development & debugging

Feature	Description
Code beautifier	Format JavaScript / CSS / HTML / XML / SQL
Code minify	Minify HTML / JS / CSS
Regular expressions	Live match and replace
Simple Postman	GET / POST / HEAD API debugging
WebSocket	Connection testing and message analysis
Userscript	Page script injection

Converters

Feature	Description
Timestamp	Unix ↔ date, multi-timezone world clock, Windows FILETIME conversion
Radix conversion	Base 2/4/8/10/16 with BigInt for large integers without loss
Color	HEX / RGB / HSL / HSV with alpha

Images & generation

Feature	Description
QR code	Generate (optional logo, colors, size) and scan/decode
Barcode	Code128 / Code39 / EAN-13 / EAN-8 / UPC / ITF-14
UUID / ID generator	UUID v4, Snowflake ID (generate + parse), NanoID
Image Base64	Image ↔ Base64
Page screenshot	Viewport / full-page scrolling capture
Color picker	Pick colors from any element
SVG conversion	SVG ↔ PNG and other formats

Other tools

Feature	Description
AI assistant	Code optimization, design, research
Mock data	Names, phones, IDs, addresses, etc.
Random password	Length and character sets
Sticky notes	Categories, import/export
Markdown	HTML → Markdown, PDF download
Poster	Multi-template posters
Charts	Multiple chart types and visualization
Page performance	Load timing analysis

---

Recent updates

v2026.04 — major improvements

New

• Barcode generation (Code128 / EAN-13 / UPC and six formats)
• UUID v4 / Snowflake ID / NanoID generator (new tool page)
• Windows FILETIME ↔ date conversion
• String escape/unescape encode/decode
• Radix conversion BigInt support (large integers without loss)

Security

• Replaced project-wide evalCore dynamic execution with safer approaches
• Fixed Toast / innerHTML XSS
• Improved Content Script injection (insertCSS instead of misused APIs)
• _codeBeautify fileType allowlist validation

Fixes

• Lossless JSON BigInt handling (pure module json-utils.js)
• Service Worker sleep (chrome.alarms instead of setTimeout)
• Content Script: document_idle + all_frames: false to fix crashes on sites like Google Meet
• Timestamp 0 validation
• Code beautifier let/const compatibility

Engineering

• Unit tests: Vitest + 79 cases
• CI/CD: GitHub Actions
• ESLint
• Removed dead dependencies and code
• Babel target Chrome 58 → 100

---

Installation

Browser stores (recommended)

Browser	Install
Chrome	Chrome Web Store
Edge	Microsoft Edge Add-ons
Firefox	Firefox Add-ons

From source

git clone https://github.com/zxlie/FeHelper.git
cd FeHelper
npm install
npm test        # run tests

Open chrome://extensions/ → Developer mode → Load unpacked → select the apps directory.

Offline install

Download CRX or ZIP from Chrome-Stats and drag onto chrome://extensions/.

---

Development

npm install          # dependencies
npm test             # Vitest unit tests
npm run test:watch   # watch mode
npm run test:coverage # coverage
npx eslint apps/     # lint

Project layout

FeHelper/
├── apps/                    # Extension source
│   ├── manifest.json        # Chrome Extension MV3 manifest
│   ├── background/          # Service Worker
│   ├── popup/               # Popup
│   ├── options/             # Settings + tool marketplace
│   ├── json-format/         # JSON formatter
│   ├── en-decode/           # Encode/decode
│   ├── timestamp/           # Timestamp
│   ├── trans-radix/         # Radix conversion
│   ├── qr-code/             # QR code + barcode
│   ├── uuid-gen/            # UUID / Snowflake ID
│   ├── code-beautify/       # Code beautifier
│   └── ...                  # More tools
├── test/                    # Vitest tests
├── .github/workflows/       # CI/CD
├── vitest.config.js
├── eslint.config.js
└── package.json

Contributing

1. Fork the repo
2. Branch: git checkout -b feature/your-feature
3. Commit: git commit -m 'Add some feature'
4. Push: git push origin feature/your-feature
5. Open a Pull Request

---

Contact

• Website: fehelper.com
• Email: xianliezhao@foxmail.com
• WeChat: 398824681
• Issues: GitHub Issues

License

MIT License

---