urllib.unquote in JavaScript

py_unquote.js

// LICENCE: BSD 3 Clause

var _hexDig = "0123456789ABCDEFabcdef";
var _hexToChar = {};
var i, j;

// generate convertion map
for(i in _hexDig){
  for(j in _hexDig){
    var key = _hexDig[i] + _hexDig[j] ;
    _hexToChar[key] = String.fromCharCode(parseInt(key, 16));
  }
}

function unquote(encoded_string){
  var bits = encoded_string.split('%');
  
  if(bits.length === 1){ 
    return encoded_string;
  }
  
  var res = [bits[0]];
  bits.slice(1).map(function(data){
    var f = data.slice(0,2);
    var val = _hexToChar[f];
    
    if(val === undefined){
      res.push('%');
      res.push(data);
    }else{
      res.push(val);
      res.push(data.slice(2));
    }
  });
  
  return res.join('');
}