base64 encode, decode

b64Enc_Dec.js

//Extend the String object with toBase64() and fromBase64() functions
//ES6..
String.prototype.toBase64 = function() {
var basechars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";
return [...this].map(c=>c.charCodeAt()).map(n=> { 
 return ((+n).toString(2).length < 8) ? "0".repeat(8-(+n).toString(2).length)+(+n).toString(2)
                                      :(+n).toString(2);
}).join("")
  .replace(/(\d)(?=(?:\d{6})+$)/g,"$1 ")
  .split(" ")
  .map(d=>parseInt(d,2))
  .map(b=>basechars.charAt(b)).join("");
}

String.prototype.fromBase64 = function() {
var baserange = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";
  var h1, h2, h3, h4, o1, o2, o3, bits, i = 0, bytes = [];

  do {
    [h1, h2, h3, h4] = [baserange.indexOf(this.charAt(i++)),baserange.indexOf(this.charAt(i++)),
                        baserange.indexOf(this.charAt(i++)),baserange.indexOf(this.charAt(i++))]
    bits = h1 << 18 | h2 << 12 | h3 << 6 | h4;
    [o1, o2, o3] = [shiftOp(bits,16,0xFF), shiftOp(bits,8,0xFF), bits & 0xFF]
    bytes.push(o1);bytes.push(o2);bytes.push(o3);
  } while (i < this.length);

  return bytes.map(d=>String.fromCharCode(d)).join("");
}
const shiftOp = (bit, byvals, rev) => bit >> byvals & rev;