Javascript / Encode and Decode using customized Regex

endcode.js

var encode = "abcdefg !@#$%^&*()"
var decode = "zyxwvut";

var swapValue = {
    a:"z",
    b:"y",
    c:"x",
    d:"w",
    e:"v",
    f:"u",
    g:"t",
    h:"s",
    i:"r",
    j:"q",
    k:"p",
    l:"o",
    m:"n",
    n:"m",
    o:"l",
    p:"k",
    q:"j",
    r:"i",
    s:"h",
    t:"g",
    u:"f",
    v:"e",
    w:"d",
    x:"c",
    y:"b",
    z:"a"
};

// cunstructed custom regular expression object with global modifier (all matches) and insensitive(case) modifier 
// swap value with join method (a - > z) 
var regEncode = new RegExp(Object.keys(swapValue).join("|"),"gi");


encode = encode.replace(regEncode, function(matched){
  return swapValue[matched.toLowerCase()];
});

var result = encode.replace(/[^a-zA-Z 0-9\s]+/g,'');

console.log(result);


/*
decode = decode.replace(regEncode, function(matched){
  return swapValue[matched.toLowerCase()];
});
*/