example to unobfuscate a variant of obfuscated javascript

unobfuscate.js

const atob = require('atob');
const fs = require('fs');
const unminify = require('unminify');

const obfuscated = require('./obfuscated').data;
const outputFile = "output.js";

let decoded = atob(obfuscated);
let escaped = escape(decoded);
let ready = decodeURIComponent(escaped);

let unobfuscated = unobfuscate(ready);
let unminified = unminify(unobfuscated)

fs.writeFile(outputFile, unminified, function(e) {
    console.log("saved")
});

function unobfuscate(_string) {
    let _dict = {},
        _array = (_string + "").split(""),
        _currentChar = _array[0],
        _offset = _currentChar,
        _result = [_currentChar],
        _count = 256,
        _predicate;

    for (let i=1; i < _array.length; i++) {
        let _nextCharCode = _array[i].charCodeAt(0);
        if (_nextCharCode < 256) {
          _predicate = _array[i];
        } else{
          _predicate = _dict[_nextCharCode] ? _dict[_nextCharCode] : (_offset + _currentChar);
        }
        _result.push(_predicate);
        _currentChar = _predicate.charAt(0);
        _dict[_count] = _offset + _currentChar;
        _count++;
        _offset = _predicate;
    }
    return _result.join("");
}