Run results for: parse hex to bytes

Run details:

User agent: Mozilla/5.0 (Linux; Android 6.0.1; Moto G (4) Build/MPJ24.139-23.4) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/52.0.2743.98 Mobile Safari/537.36

Browser: Chrome Mobile 52

Operating system: Android 6.0.1

Device Platform: Moto G

Date tested: 8 years ago

Test name	Executions per second
original	113.1 Ops/sec
ES5 replace match map	26.8 Ops/sec
match without replace	39.8 Ops/sec
iteration with replace	21.9 Ops/sec
looping with exec	43.9 Ops/sec
non regex	274.8 Ops/sec

Script Preparation code:

function test(bin, bytes){
	var r, i;
	hex = '', chars = '\n: -';
	//generate an array of random octets and
	//a corresponding hex string
	for(i = 0; i < bytes; i++){
		r = Math.random() * 0x100 | 0,
		bin[i] = (r & 0xff);
		hex += (r >> 4).toString(16) + (r & 0xf).toString(16);
	}
	//insert non-hex characters at random positions in hex string
	for(i = 0; i < 10; i++){
		r = Math.random() * hex.length | 0;
		hex = hex.slice(0, r) + chars.charAt(r & 3) + hex.slice(r);
	}
  return hex;
}

var expected = [],
    testCase = test(expected, 10000);

function parseHex1(hex){// original
    hex = hex.replace(/[^0-9a-fA-F]/g, '');
    var i, 
        len = hex.length, 
        bin = [];
    for(i = 0; i < len - 1; i += 2){
        bin.push(+('0x' + hex.substring(i, i + 2)));
    }
    return bin;
}

function parseHex2(string) {// replace match map ES5
  return string.replace(/[^0-9a-fA-F]/g, '').match(/[0-9a-fA-F]{2}/g).map(function(hex) {
    return parseInt(hex, 16);
  });
}

function parseHex3(hex){//match without replace
		hex = hex.match(/[\da-f]/gi);
		for(var i = 0; i < hex.length - 1; i += 2){
			hex[i >> 1] = +('0x' + hex[i] + hex[i + 1]);
		}
		hex.length = i >> 1;
		return hex;
}


function parseHex4(hex){// iteration with replace
 		var bin = [];
		hex.replace(/([\da-f])[^\da-f]*([\da-f])/gi,
			function(m, digit1, digit2){
				bin.push(+('0x' + digit1 + digit2));
			}
		);
		return bin;
}

function parseHex5(hex){// looping with exec
		var bin = [],
			regex = /([\da-f])[^\da-f]*([\da-f])/gi,
			result;
		while(result = regex.exec(hex)){
			bin.push(+('0x' + result[1] + result[2]));
		}
		return bin;
}

function parseHex6(hex){// non regex
	var bin = [], i, c, isEmpty = 1, buffer;
	for(i = 0; i < hex.length; i++){
		c = hex.charCodeAt(i);
		if(c > 47 && c < 58 || c > 64 && c < 71 || c > 96 && c < 103){
			buffer = buffer << 4 ^ (c > 64 ? c + 9 : c) & 15;
			if(isEmpty ^= 1){
				bin.push(buffer & 0xff);
			}
		}
	}
	return bin;
}

Tests:

original
parseHex1(testCase);
ES5 replace match map
parseHex2(testCase);
match without replace
parseHex3(testCase);
iteration with replace
parseHex4(testCase);
looping with exec
parseHex5(testCase);
non regex
parseHex6(testCase);

Run results for: parse hex to bytes

original

ES5 replace match map

match without replace

iteration with replace

looping with exec

non regex