Reversing Obfuscated JavaScript

Client-side JavaScript ships the whole program to the reader — there is no stripped binary here, only code deliberately made unreadable. That changes the job: you are almost never recovering missing information, you are undoing a transformation. Identify the transformation first, reverse it with the tool built for it, and fall back to hand-written AST passes only for the custom layer no off-the-shelf tool knows.

When to Use

• A page or extension ships a large minified/bundled .js you need to read
• Code is full of _0x1234 identifiers, a big string array, and a rotation IIFE at the top — the obfuscator.io signature
• A .js.map sourcemap is reachable, or webpack left //# sourceMappingURL
• You must locate where a request signature, HMAC, token, or crypto key is computed inside a running bundle
• Reproducing a client-side algorithm (an anti-bot signal, a licence check, a paywall gate) from the shipped code