A Super simple encryption cipher using XOR and Base64 in JavaScript - Just made the typescript version for angular 4, and I removed the underscore dependency

XORCipher.ts

// XORCipher - Super simple encryption using XOR and Base64
// Usage
// --------
//
//     XORCipher.encode("test", "foobar");   // => "EgocFhUX"
//     XORCipher.decode("test", "EgocFhUX"); // => "foobar"
//
// Copyright © 2013 Devin Weaver <suki@tritarget.org>
//
// This program is free software. It comes without any warranty, to
// the extent permitted by applicable law. You can redistribute it
// and/or modify it under the terms of the Do What The Fuck You Want
// To Public License, Version 2, as published by Sam Hocevar. See
// http://www.wtfpl.net/ for more details.

export class XORCipher {

  public encode(key:string, data:string):string {
    data = this.xor_encrypt(key, data);
    return this.b64_encode(data);
  }

  public decode(key:string, data:string):string {
    data = this.b64_decode(data);
    return this.xor_decrypt(key, data);
  }

  private b64_table = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";

  private b64_encode(data) {
    let o1, o2, o3, h1, h2, h3, h4, bits, r, i = 0, enc = "";
    if (!data) {
      return data;
    }
    do {
      o1 = data[i++];
      o2 = data[i++];
      o3 = data[i++];
      bits = o1 << 16 | o2 << 8 | o3;
      h1 = bits >> 18 & 0x3f;
      h2 = bits >> 12 & 0x3f;
      h3 = bits >> 6 & 0x3f;
      h4 = bits & 0x3f;
      enc += this.b64_table.charAt(h1) + this.b64_table.charAt(h2) + this.b64_table.charAt(h3) + this.b64_table.charAt(h4);
    } while (i < data.length);
    r = data.length % 3;
    return (r ? enc.slice(0, r - 3) : enc) + "===".slice(r || 3);
  }

  private b64_decode(data) {
    let o1, o2, o3, h1, h2, h3, h4, bits, i = 0, result = [];
    if (!data) {
      return data;
    }
    data += "";
    do {
      h1 = this.b64_table.indexOf(data.charAt(i++));
      h2 = this.b64_table.indexOf(data.charAt(i++));
      h3 = this.b64_table.indexOf(data.charAt(i++));
      h4 = this.b64_table.indexOf(data.charAt(i++));
      bits = h1 << 18 | h2 << 12 | h3 << 6 | h4;
      o1 = bits >> 16 & 0xff;
      o2 = bits >> 8 & 0xff;
      o3 = bits & 0xff;
      result.push(o1);
      if (h3 !== 64) {
        result.push(o2);
        if (h4 !== 64) {
          result.push(o3);
        }
      }
    } while (i < data.length);
    return result;
  }

  private keyCharAt(key, i) {
    return key.charCodeAt(Math.floor(i % key.length));
  }

  private xor_encrypt(key, data) {
    return Array.prototype.map.call(data,(c, i)=>{
        return c.charCodeAt(0) ^ this.keyCharAt(key, i);
      })
  }

  private xor_decrypt(key, data) {
    return Array.prototype.map.call(data,(c, i)=>{
      return String.fromCharCode(c ^ this.keyCharAt(key, i));
    }).join("");
  }


}