Run results for: array buffer to hex conversion 8 methods vs base64 2 methods

Test name	Executions per second
✓ string +	5,316,500 Ops/sec
string + 2	5,316,376 Ops/sec
string + pad	4,910,442 Ops/sec
base64 loop	4,347,946 Ops/sec
push values	3,418,330 Ops/sec
base64	3,353,757 Ops/sec
directly set	2,449,344 Ops/sec
buf2hex()	1,701,248 Ops/sec
array prototype map	1,193,147 Ops/sec
precomputed ASCII with shift	864,891 Ops/sec

Script Preparation code:

var saltVal = crypto.getRandomValues(new Uint8Array(16));

function arrayBufferToHexString(bytes) {
    bytes = new Uint8Array(bytes);
    var hex = new Array(bytes.length);
    for (let i = 0; i < bytes.length; i++) {
        hex[i] = ("0" + bytes[i].toString(16)).slice(-2);
    }
    return hex.join("");
}

function bytesToHexString(bytes) {
    bytes = new Uint8Array(bytes);
    var hexBytes = [];
    for (var i = 0; i < bytes.length; i++) {
        var byteString = bytes[i].toString(16);
        if (byteString.length < 2) byteString = "0" + byteString;
        hexBytes.push(byteString);
    }
    return hexBytes.join("");
}

function buf2hex(buffer) { // buffer is an ArrayBuffer
  return [...new Uint8Array(buffer)]
      .map(x => x.toString(16).padStart(2, '0'))
      .join('');
}

function hex(arrayBuffer)
{
  	const asciiCodes = new Uint8Array(
    	Array.prototype.map.call(
        	"0123456789abcdef",
        	char => char.charCodeAt()
    	)
	);
  
    const buff = new Uint8Array(arrayBuffer);
    const charCodes = new Uint8Array(buff.length * 2);

    for (let i = 0; i < buff.length; ++i)
    {
        charCodes[i * 2] = asciiCodes[buff[i] >>> 4];
        charCodes[i * 2 + 1] = asciiCodes[buff[i] & 0xf];
    }

    return String.fromCharCode(...charCodes);
}

function hex2(arrayBuffer)
{
    return Array.prototype.map.call(
        new Uint8Array(arrayBuffer),
        n => n.toString(16).padStart(2, "0")
    ).join("");
}

function arrayBufferToBase64(buffer) {
  const byteArray = new Uint8Array(buffer);
  const binaryString = byteArray.reduce((acc, byte) => acc + String.fromCharCode(byte), "");
  return btoa(binaryString);
}

function arrayBufferToBase64loop( buffer ) {
    var binary = '';
    var bytes = new Uint8Array( buffer );
    var len = bytes.byteLength;
    for (var i = 0; i < len; i++) {
        binary += String.fromCharCode( bytes[ i ] );
    }
    return window.btoa( binary );
}

function bytesToHexString2(bytes) {
    bytes = new Uint8Array(bytes);
    var hexBytes = '';
    for (var i = 0; i < bytes.length; i++) {
        var byteString = bytes[i].toString(16);
        if (byteString.length < 2) byteString = "0" + byteString;
        hexBytes += byteString;
    }
    return hexBytes;
}

function bytesToHexString3(bytes) {
    bytes = new Uint8Array(bytes);
    var hexBytes = '';
    for (var i = 0; i < bytes.length; i++) {
        var byteString = bytes[i].toString(16);
        if (byteString.length < 2) hexBytes += "0";
        hexBytes += byteString;
    }
    return hexBytes;
}

function bytesToHexString4(bytes) {
    bytes = new Uint8Array(bytes);
    var hexBytes = '';
    for (var i = 0; i < bytes.length; i++) {
        hexBytes += bytes[i].toString(16).padStart(2, '0');
    }
    return hexBytes;
}

Run results for: array buffer to hex conversion 8 methods vs base64 2 methods

convert array buffer to hex

directly set

push values

buf2hex()

precomputed ASCII with shift

array prototype map

base64

base64 loop

string +

string + 2

string + pad