XOR Cipher encryption in JavaScript

xorcipher.js

const XORCipher = {
    encode(key, data) {
        data = xor_encrypt(key, new String(data).split(""));
        return b64_encode(data);
    },
    decode(key, data) {
        data = b64_decode(data);
        return xor_decrypt(key, new String(data).split(""));
    }
};

const b64_table = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";

function b64_encode(data) {
    let o1;
    let o2;
    let o3;
    let h1;
    let h2;
    let h3;
    let h4;
    let bits;
    let r;
    let i = 0;
    let 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 += b64_table.charAt(h1) + b64_table.charAt(h2) + b64_table.charAt(h3) + b64_table.charAt(h4);
    } while (i < data.length);
    r = data.length % 3;
    return (r ? enc.slice(0, r - 3) : enc) + "===".slice(r || 3);
}

function b64_decode(data) {
    let o1;
    let o2;
    let o3;
    let h1;
    let h2;
    let h3;
    let h4;
    let bits;
    let i = 0;
    const result = [];
    if (!data) {
        return data;
    }
    data += "";
    do {
        h1 = b64_table.indexOf(data.charAt(i++));
        h2 = b64_table.indexOf(data.charAt(i++));
        h3 = b64_table.indexOf(data.charAt(i++));
        h4 = 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;
}

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

function xor_encrypt(key, data) {
    return data.map((c, i) => c.charCodeAt(0) ^ keyCharAt(key, i));
}

function xor_decrypt(key, data) {
    return data.map((c, i) => String.fromCharCode(c ^ keyCharAt(key, i))).join("");
}

// from https://gist.github.com/arguiot/87de070dbf3e47c2878480b767b3665b

function encode(key: string, data: string) {
  const encrypted = xor_encrypt(key, new String(data).split(""))
  return b64_encode(encrypted)
}

function decode(key: string, data: string) {
  const decoded = b64_decode(data)
  return xor_decrypt(key, decoded)
}

const b64_table =
  "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/="

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

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

function keyCharAt(key: string, i: number) {
  return key.charCodeAt(Math.floor(i % key.length))
}

function xor_encrypt(key: string, data: string[]) {
  return data.map((c, i) => c.charCodeAt(0) ^ keyCharAt(key, i))
}

function xor_decrypt(key: string, data: number[]) {
  return data.map((c, i) => String.fromCharCode(c ^ keyCharAt(key, i))).join("")
}

export { encode, decode }