dj

dj - Dynamic JS File Extractor

中文 | English

dj intelligently detects dynamically loaded JavaScript files by statically analyzing website HTML and JS code, including webpack chunks, import() lazy loading, and more.

Features

• Deep analysis of website HTML and JS to extract dynamically loaded JavaScript files
• Smart detection of dynamic loading patterns: import(), require(), webpack chunks, vite preload, etc.
• Support for multiple frontend framework chunk mappings: Next.js, Nuxt.js, Vite, SvelteKit, Webpack, and more
• Automatic Source Map discovery
• Custom User-Agent and proxy support
• Multiple output formats: text, JSON, markdown

Installation

go install (recommended)

go install github.com/ejfkdev/dj@latest

Build from source

git clone https://github.com/ejfkdev/dj.git
cd dj
go build -ldflags="-X main.version=1.0.0" -o dj ./cmd/main.go

Download prebuilt binaries

Visit the Releases page to download binaries for your platform.

Usage

dj [options] <URL>

Basic usage

# Extract JS URLs (real-time output)
dj https://example.com

# Output in JSON format
dj -f json https://example.com

# Output in Markdown format
dj -f md https://example.com

Command line options

Examples

# Custom User-Agent
dj --useragent="Mozilla/5.0 (iPhone; CPU iPhone OS 14_0 like Mac OS X) ..." https://example.com

# Use proxy
dj --proxy="http://127.0.0.1:7890" https://example.com

# Enable debug mode
dj --debug https://example.com

Tested websites

dj https://docs.qq.com
dj https://vue.ruoyi.vip
dj https://gitee.com
dj https://nuxt.com.cn
dj https://chat.z.ai
dj https://show.cool-admin.com/login
dj https://demo.1panel.cn

Supported patterns and frameworks (16 plugins)

How it works

1. Download the target webpage HTML
2. Launch plugin analysis - each URL is processed concurrently by a goroutine:
   • Download JS content
   • Detect Content-Type (skip static resources returning HTML)
   • Dispatch to all plugins for pattern matching
3. Plugins discover new JS URLs or path fragments, add to processing queue
4. Probe for Source Map files (via sourceMappingURL or HTTP header)
5. Collect all discovered JS URLs and output

Output formats

Text (default)

https://example.com/js/main.js
https://example.com/js/chunk-abc123.js
https://example.com/js/async-def456.js

JSON

{
  "summary": {
    "jsCount": 3,
    "sourceMapCount": 1
  },
  "jsURLs": [
    "https://example.com/js/main.js",
    "https://example.com/js/chunk-abc123.js"
  ],
  "cacheBase": "/tmp/ejfkdev/dj/example.com",
  "cacheDirs": {
    "js": "/tmp/ejfkdev/dj/example.com/js",
    "sourceMap": "/tmp/ejfkdev/dj/example.com/source_map",
    "html": "/tmp/ejfkdev/dj/example.com/html/web.html"
  }
}

Caching

Caching is enabled by default. Cache is stored in the system temp directory:

Cache structure:

<temp_dir>/ejfkdev/dj/<origin>/
├── js/                    # Downloaded JS files
├── source_map/            # Source Map files
├── html/                  # Original HTML
└── meta.json             # Site metadata

FAQ

Why aren't some dynamically loaded JS files being extracted?

This tool uses static analysis of JS code to detect dynamic loading patterns. If a website uses special loading methods, they may not be covered. If you find a website whose dynamic JS cannot be extracted, feel free to submit an Issue with the site URL and any relevant code clues.

License

MPL 2.0 (Mozilla Public License)