Run results for: base64 or json deserialization benchmark

Run details:

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 11_1_0) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/87.0.4280.88 Safari/537.36

Browser: Chrome 87

Operating system: Mac OS X 11.1.0

Device Platform: Desktop

Date tested: 3 years ago

Test name	Executions per second
jsonParse	995.3 Ops/sec
danguer	223.0 Ops/sec
niklasvh	49.5 Ops/sec
typedArrayFrom	43.4 Ops/sec

Script Preparation code:

var ab = new ArrayBuffer(50*1024);
var uint8 = new Uint8Array(ab);
for (var i = 0; i < ab.byteLength; i++) {
    uint8[i] = i % 256;
}
var b64 = btoa(uint8)
var json = JSON.stringify([...uint8]);

function byteArrayToString(bytes) {
  var CHUNK_SIZE = 8*1024;
  if (bytes.length <= CHUNK_SIZE)
    return String.fromCharCode.apply(null, bytes);
  var str = '';
  for (var i = 0; i < bytes.length; i += CHUNK_SIZE)
    str += String.fromCharCode.apply(null, bytes.slice(i, i+CHUNK_SIZE));
  return str;
}

function validate(res){
  if (res !== expected)
      throw "expected=" + expected + " but got " + res;
}


function typedArrayFrom(base64_string) {
    return Uint8Array.from(atob(base64_string), c => c.charCodeAt(0))
}

function jsonParse(jsonStr) {
    return Uint8Array.from(JSON.parse(jsonStr))
}

var chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";

// Use a lookup table to find the index.
var lookup = new Uint8Array(256);
for (var i = 0; i < chars.length; i++) {
  lookup[chars.charCodeAt(i)] = i;
}

var niklasvh =  function(base64) {
  var bufferLength = base64.length * 0.75,
  len = base64.length, i, p = 0,
  encoded1, encoded2, encoded3, encoded4;

  if (base64[base64.length - 1] === "=") {
    bufferLength--;
    if (base64[base64.length - 2] === "=") {
      bufferLength--;
    }
  }

  var arraybuffer = new ArrayBuffer(bufferLength),
  bytes = new Uint8Array(arraybuffer);

  for (i = 0; i < len; i+=4) {
    encoded1 = lookup[base64.charCodeAt(i)];
    encoded2 = lookup[base64.charCodeAt(i+1)];
    encoded3 = lookup[base64.charCodeAt(i+2)];
    encoded4 = lookup[base64.charCodeAt(i+3)];

    bytes[p++] = (encoded1 << 2) | (encoded2 >> 4);
    bytes[p++] = ((encoded2 & 15) << 4) | (encoded3 >> 2);
    bytes[p++] = ((encoded3 & 3) << 6) | (encoded4 & 63);
  }

  return arraybuffer;
};

var danguer = {
	_keyStr : "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=",
	
	/* will return a  Uint8Array type */
	decodeArrayBuffer: function(input) {
		var bytes = (input.length/4) * 3;
		var ab = new ArrayBuffer(bytes);
		this.decode(input, ab);
		
		return ab;
	},

	removePaddingChars: function(input){
		var lkey = this._keyStr.indexOf(input.charAt(input.length - 1));
		if(lkey == 64){
			return input.substring(0,input.length - 1);
		}
		return input;
	},

	decode: function (input, arrayBuffer) {
		//get last chars to see if are valid
		input = this.removePaddingChars(input);
		input = this.removePaddingChars(input);

		var bytes = parseInt((input.length / 4) * 3, 10);
		
		var uarray;
		var chr1, chr2, chr3;
		var enc1, enc2, enc3, enc4;
		var i = 0;
		var j = 0;
		
		if (arrayBuffer)
			uarray = new Uint8Array(arrayBuffer);
		else
			uarray = new Uint8Array(bytes);
		
		input = input.replace(/[^A-Za-z0-9\+\/\=]/g, "");
		
		for (i=0; i<bytes; i+=3) {	
			//get the 3 octects in 4 ascii chars
			enc1 = this._keyStr.indexOf(input.charAt(j++));
			enc2 = this._keyStr.indexOf(input.charAt(j++));
			enc3 = this._keyStr.indexOf(input.charAt(j++));
			enc4 = this._keyStr.indexOf(input.charAt(j++));
	
			chr1 = (enc1 << 2) | (enc2 >> 4);
			chr2 = ((enc2 & 15) << 4) | (enc3 >> 2);
			chr3 = ((enc3 & 3) << 6) | enc4;
	
			uarray[i] = chr1;			
			if (enc3 != 64) uarray[i+1] = chr2;
			if (enc4 != 64) uarray[i+2] = chr3;
		}
	
		return uarray;	
	}
}

Tests:

jsonParse
jsonParse(json)
danguer
danguer.decodeArrayBuffer(b64)
niklasvh
niklasvh(b64)
typedArrayFrom
typedArrayFrom(b64)