Zero width space decoder. beware!

data.md

​‌‌​​​‌‌​‌‌​‌‌‌‌​‌‌​‌‌‌​​‌‌‌​​‌‌​‌‌​‌‌‌‌​‌‌​‌‌​​​‌‌​​‌​‌​​‌​‌‌‌​​‌‌​‌‌​​​‌‌​‌‌‌‌​‌‌​​‌‌‌​​‌​‌​​​​‌‌​‌‌​​​‌‌​‌‌‌‌​‌‌​​​‌‌​‌‌​​​​‌​‌‌​‌‌​​​‌​‌​​‌‌​‌‌‌​‌​​​‌‌​‌‌‌‌​‌‌‌​​‌​​‌‌​​​​‌​‌‌​​‌‌‌​‌‌​​‌​‌​​‌​‌​​‌

data.txt

​‌‌​​​‌‌​‌‌​‌‌‌‌​‌‌​‌‌‌​​‌‌‌​​‌‌​‌‌​‌‌‌‌​‌‌​‌‌​​​‌‌​​‌​‌​​‌​‌‌‌​​‌‌​‌‌​​​‌‌​‌‌‌‌​‌‌​​‌‌‌​​‌​‌​​​​‌‌​‌‌​​​‌‌​‌‌‌‌​‌‌​​​‌‌​‌‌​​​​‌​‌‌​‌‌​​​‌​‌​​‌‌​‌‌‌​‌​​​‌‌​‌‌‌‌​‌‌‌​​‌​​‌‌​​​​‌​‌‌​​‌‌‌​‌‌​​‌​‌​​‌​‌​​‌

gistfile1.js

const chunk = (arr, len) => {
  var chunks = [],i = 0,n = arr.length;
  while (i < n) {
    chunks.push(arr.slice(i, i += len));
  }
  return chunks;
}

const encode = x => [...x].map(x => x.charCodeAt(0)).map((x,i) => { if (x >= 255) { throw new Error('Found non ascii character at position: ' + i) } return [...x.toString(2).padStart(8, 0)].map(x => x === '0' ? String.fromCharCode(8203) : String.fromCharCode(8204) ).join('')   }).join('');
const decode = x => chunk(x.split(''), 8).map(x => parseInt(x.map(x => x === String.fromCharCode(8203) ? 0 : 1 ).join(''), 2) ).map(x => String.fromCharCode(x)).join('');

poc.js

var data =  encode('console.log(localStorage)')

console.log(data)

eval(decode(data))

test.js

var data = '​‌‌​​​‌‌​‌‌​‌‌‌‌​‌‌​‌‌‌​​‌‌‌​​‌‌​‌‌​‌‌‌‌​‌‌​‌‌​​​‌‌​​‌​‌​​‌​‌‌‌​​‌‌​‌‌​​​‌‌​‌‌‌‌​‌‌​​‌‌‌​​‌​‌​​​​‌‌​‌‌​​​‌‌​‌‌‌‌​‌‌​​​‌‌​‌‌​​​​‌​‌‌​‌‌​​​‌​‌​​‌‌​‌‌‌​‌​​​‌‌​‌‌‌‌​‌‌‌​​‌​​‌‌​​​​‌​‌‌​​‌‌‌​‌‌​​‌​‌​​‌​‌​​‌';

eval(decode(data));

without eval.js

0.0.constructor.constructor(decode(data))()

// Soooo you need to be able to control two property access, and the argument passed to a function, with user input.
// Or you hide and obfuscate that on a large codebase with tons of layers of indirection, and done!
// But you also need the encoder/decoder implementation, so its kinda pointless