Javascript Deobfuscation

Obfuscation

We can view the source code of a webpage using Developer Tools (Ctrl+U to view page source); JS can be written internally between <script> tags, or into separate '.js' file & referenced in HTML code.
Obfuscation - technique used to make script more difficult to be read; usually done by obfuscation tools.
Code minification - having entire code in a single line, saved with extension .min.js; we can use tools like javascript-minifier for this.
For obfuscation, we can use tools such as BeautifyTools - this uses packing techniques, which usually convert all characters of code into a list/dictionary, and then refer to them using a function to rebuild original code.
obfuscator.io is another tool in which we can modify obfuscation settings such as encoding and rotation so that we don't get any remnants of the original code; other tools include JSF, jjencode and aaencode.

To beautify minified JS code, we can use tools like Browser Dev Tools, Prettier and Beautifier.
To deobfuscate packed code, we can use tools like UnPacker.
Encoding & decoding is another common method used as part of obfuscation/deobfuscation:
- base64 - echo <string> | base64 to encode and echo <string> | base64 -d to decode
- hex - echo <string> | xxd -p and echo <string> | xxd -p -r for hex encoding & decoding
- rot13 (caesar) - use online tools like CyberChef