This is an snippet I saved back in college. I’m not sure who the original author is for this. Let’s try to understand how this works

// A decimal to binary convertor
// All Credits to the original author
(_$=($,_=[]+[])=>$?_$($>>+!![],($&+!![])+_):_)(255);

Round 1

Let’s format this

(
  _$=($,_=[]+[]) => {
    return $?_$($>>+!![],($&+!![])+_):_
  }
)(255);

Round 2

Rename to some readable variables

// number is the number we are trying to convert to binary
// binary is the binary representation constructed so far
(
  fn = (number, binary=[]+[]) => {
    return number ? fn(number>>+!![],(number&+!![])+binary) : binary
  }
)(255);

Round 3

Simplyfing some expressions

// []+[] === ''
// !![] === true
// +true === 1
// (number&1) + '' === '0' | '1'
(
  fn = (number, binary = "") => {
    return number ? fn(number >> 1, (number & 1) + binary) : binary;
  }
)(255);

Round 4

Simplyfing this down even further. Now this is a standard recursive decimal to binary convertor

// From this (_$=($,_=[]+[])=>$?_$($>>+!![],($&+!![])+_):_)(255); to 
const fn = (number, binary = "") => {
  if (number) {
    binary = (number & 1) + binary;
    number >>= 1;
    return fn(number, binary);
  }
  return binary;
};
fn(255);