HEX to Base64 converter for JavaScript

Question

Anyone know of a good snippet of JavaScript code to convert HEX encoded strings to base64 encoded strings?

Answer 1

If you're working in Node or using Browserify, you can use

var base64String = Buffer.from(hexString, 'hex').toString('base64')

or

var hexString = Buffer.from(base64String, 'base64').toString('hex')

Answer 2

if (!window.atob) {
  var tableStr = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
  var table = tableStr.split("");

  window.atob = function (base64) {
    if (/(=[^=]+|={3,})$/.test(base64)) throw new Error("String contains an invalid character");
    base64 = base64.replace(/=/g, "");
    var n = base64.length & 3;
    if (n === 1) throw new Error("String contains an invalid character");
    for (var i = 0, j = 0, len = base64.length / 4, bin = []; i < len; ++i) {
      var a = tableStr.indexOf(base64[j++] || "A"), b = tableStr.indexOf(base64[j++] || "A");
      var c = tableStr.indexOf(base64[j++] || "A"), d = tableStr.indexOf(base64[j++] || "A");
      if ((a | b | c | d) < 0) throw new Error("String contains an invalid character");
      bin[bin.length] = ((a << 2) | (b >> 4)) & 255;
      bin[bin.length] = ((b << 4) | (c >> 2)) & 255;
      bin[bin.length] = ((c << 6) | d) & 255;
    };
    return String.fromCharCode.apply(null, bin).substr(0, bin.length + n - 4);
  };

  window.btoa = function (bin) {
    for (var i = 0, j = 0, len = bin.length / 3, base64 = []; i < len; ++i) {
      var a = bin.charCodeAt(j++), b = bin.charCodeAt(j++), c = bin.charCodeAt(j++);
      if ((a | b | c) > 255) throw new Error("String contains an invalid character");
      base64[base64.length] = table[a >> 2] + table[((a << 4) & 63) | (b >> 4)] +
                              (isNaN(b) ? "=" : table[((b << 2) & 63) | (c >> 6)]) +
                              (isNaN(b + c) ? "=" : table[c & 63]);
    }
    return base64.join("");
  };

}

function hexToBase64(str) {
  return btoa(String.fromCharCode.apply(null,
    str.replace(/\r|\n/g, "").replace(/([\da-fA-F]{2}) ?/g, "0x$1 ").replace(/ +$/, "").split(" "))
  );
}

function base64ToHex(str) {
  for (var i = 0, bin = atob(str.replace(/[ \r\n]+$/, "")), hex = []; i < bin.length; ++i) {
    var tmp = bin.charCodeAt(i).toString(16);
    if (tmp.length === 1) tmp = "0" + tmp;
    hex[hex.length] = tmp;
  }
  return hex.join(" ");
}

Answer 3

The excellent comment by @dandavis is modified by StackOverflow, and has some weird hidden characters.

Here it is as one liner :

btoa("a6b580481008e60df9350de170b7e728".match(/\w{2}/g).map(function(a){return String.fromCharCode(parseInt(a, 16));} ).join(""))

or :

function hexToBase64(hexstring) {
    return btoa(hexstring.match(/\w{2}/g).map(function(a) {
        return String.fromCharCode(parseInt(a, 16));
    }).join(""));
}

hexToBase64("a6b580481008e60df9350de170b7e728");

Both return :

"prWASBAI5g35NQ3hcLfnKA=="

Note that the hex string should have an even length :

hexToBase64("00");
// => "AA=="
hexToBase64("000");
// => "AA=="

Answer 4

I liked the approach from @eric-duminil nevertheless the solution below - avoiding regex - is ~2x faster.

Browser:

function hexToBase64(hexStr) {
  return btoa([...hexStr].reduce((acc, _, i) =>
    acc += !(i - 1 & 1) ? String.fromCharCode(parseInt(hexStr.substring(i - 1, i + 1), 16)) : "" 
  ,""));
}

OR

// even a bit faster
function hexToBase64(hexStr) {
 let base64 = "";
 for(let i = 0; i < hexStr.length; i++) {
   base64 += !(i - 1 & 1) ? String.fromCharCode(parseInt(hexStr.substring(i - 1, i + 1), 16)) : ""
 }
 return btoa(base64);
}

Node:

const base64 = Buffer.from(hexStr, 'hex').toString('base64');

Answer 5

Large strings, no btoa

Solution below is good for large strings - if you want to get bytes from base64 then look HERE

function bytesArrToBase64(arr) {
  const abc = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"; // base64 alphabet
  const bin = n => n.toString(2).padStart(8,0); // convert num to 8-bit binary string
  const l = arr.length
  let result = '';

  for(let i=0; i<=(l-1)/3; i++) {
    let c1 = i*3+1>=l; // case when "=" is on end
    let c2 = i*3+2>=l; // case when "=" is on end
    let chunk = bin(arr[3*i]) + bin(c1? 0:arr[3*i+1]) + bin(c2? 0:arr[3*i+2]);
    let r = chunk.match(/.{1,6}/g).map((x,j)=> j==3&&c2 ? '=' :(j==2&&c1 ? '=':abc[+('0b'+x)]));  
    result += r.join('');
  }

  return result;
}

function hexToBytes(hexString) {
  return hexString.match(/.{1,2}/g).map(x=> +('0x'+x));
}


// ---------
// TEST
// ---------
let hexString = "a6b580481008e60df9350de170b7e728";
let bytes = hexToBytes(hexString);
let base64 = bytesArrToBase64(bytes);

console.log(base64);