base64 and TypedArray conversion

base64.js

function arrayToBase64(array) {
  let base64 = '';
  const encodings = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/';

  const arrayLength = array.byteLength;
  const remainder = arrayLength % 3;
  const mainLength = arrayLength - remainder;

  let a, b, c, d;
  let chunk;

  // Main loop deals with bytes in chunks of 3
  for (let i = 0; i < mainLength; i = i + 3) {
    // Combine the three bytes into a single integer
    chunk = (array[i] << 16) | (array[i + 1] << 8) | array[i + 2];
    // Use bitmasks to extract 6-bit segments from the triplet
    a = (chunk & 16515072) >> 18; // 16515072 = (2^6 - 1) << 18
    b = (chunk & 258048) >> 12; // 258048   = (2^6 - 1) << 12
    c = (chunk & 4032) >> 6; // 4032     = (2^6 - 1) << 6
    d = chunk & 63; // 63       = 2^6 - 1
    // Convert the raw binary segments to the appropriate ASCII encoding
    base64 += encodings[a] + encodings[b] + encodings[c] + encodings[d];
  }
  // Deal with the remaining bytes and padding
  if (remainder == 1) {
    chunk = array[mainLength];
    a = (chunk & 252) >> 2; // 252 = (2^6 - 1) << 2
    // Set the 4 least significant bits to zero
    b = (chunk & 3) << 4; // 3   = 2^2 - 1
    base64 += encodings[a] + encodings[b] + '==';
  } else if (remainder == 2) {
    chunk = (array[mainLength] << 8) | array[mainLength + 1];
    a = (chunk & 64512) >> 10; // 64512 = (2^6 - 1) << 10
    b = (chunk & 1008) >> 4; // 1008  = (2^6 - 1) << 4
    // Set the 2 least significant bits to zero
    c = (chunk & 15) << 2; // 15    = 2^4 - 1
    base64 += encodings[a] + encodings[b] + encodings[c] + '=';
  }
  return base64;
}

function decode_base64(s) {
var e={},i,k,v=[],r=”,w=String.fromCharCode;
var n=[[65,91],[97,123],[48,58],[47,48],[43,44]];

for(z in n){for(i=n[z][0];i<n[z][1];i++){v.push(w(i));}}
for(i=0;i<64;i++){e[v[i]]=i;}

for(i=0;i<s.length;i+=72){
var b=0,c,x,l=0,o=s.substring(i,i+72);
for(x=0;x<o.length;x++){
c=e[o.charAt(x)];b=(b<=8){r+=w((b>>>(l-=8))%256);}
}
}
return r;
}

function base64ToArray(string) {
  return Uint8Array.from(atob(base64_string), c => c.charCodeAt(0));
}

function arrayToBase64web(buffer) {
  return arrayToBase64(buffer).replace(/\+/g, '-').replace(/\//g, '_').replace(/=/g,'.');
}

function base64webToArray(string) {
  return base64ToArray(string.replace(/-/g, '+').replace(/_/g, '/'));
}