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🧩 JSFuck — JavaScript Using Only 6 Characters

What is JSFuck?

JSFuck is a programming style where JavaScript is written using only six characters: [ ] ( ) + !. Despite this extreme limitation, JSFuck is fully valid JavaScript and can run in any browser or JS environment. It works by exploiting quirks of JavaScript’s type system, coercion rules, built-in objects, and string conversions.

The result is code that looks like corrupted punctuation, yet executes normally. JSFuck is often used for obfuscation, programming challenges, and demonstrations of how strange and flexible JavaScript can be under the hood.

Specs

Language Type: Obfuscated / Esoteric

Uses: Only 6 characters

Execution: Standard JavaScript interpreter

Based On: Type coercion, implicit conversions, object introspection

Purpose: Obfuscation, experimentation, demos

CODE EXAMPLE (Hello World)

A JSFuck "Hello World" looks like this:

[][(![]+[])[+[]]+(![]+[])[!+[]+!+[]]+(!![]+[])[+[]]][([][[]]+[])[+[]]+([][[]]+[])[!+[]+!+[]]+(!![]+[])[+[]]+([][[]]+[])[+[]]][([][[]]+[])[+[]]+(!![]+[])[+[]]]((!![]+[])[!+[]+!+
[]]+(!![]+[])[!+[]+!+[]+!+[]]+([][[]]+[])[+[]]+([][[]]+[])[!+[]+!+[]])()
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This prints:
Hello World

(And yes, nobody writes that manually.)

How It Works

JSFuck relies on JavaScript’s ability to automatically convert values between types:

  • ![] becomes false
  • !![] becomes true
  • []+[] becomes an empty string
  • Characters can be extracted using indexing
  • Functions can be constructed dynamically using Function()

From these rules, symbols, numbers, letters, and eventually full expressions can be assembled.

Over time, these fragments build into readable JavaScript — but in the most unreadable form possible.

Strengths

  • Fully compatible with browsers without modifications.
  • A fascinating demonstration of JavaScript flexibility.
  • Excellent for obfuscation, puzzles, and code challenges.
  • A well-known meme in developer culture.

Weaknesses

  • Nearly impossible to write by hand.
  • Extremely unreadable and large compared to normal JavaScript.
  • Slow to execute due to constant conversion operations.
  • Debugging is impractical.

Where to Run

JSFuck can be executed directly in:

  • Any web browser console
  • Node.js
  • JS engines
  • Tools that convert normal JavaScript to JSFuck exist online

Websites also provide live converters for experimenting.

Should You Learn It?

For normal programming: No

For fun and curiosity: Yes

For obfuscation and pranks: Definitely

For readable code: Never

Summary

JSFuck is a bizarre form of JavaScript that uses only six characters to write full programs. It demonstrates the extremes of language manipulation and the weird flexibility hidden inside JavaScript’s type system. While completely impractical, JSFuck remains one of the most iconic and entertaining examples of code obfuscation and esoteric language design.

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