Run results for: Fetch cookie value

Test name	Executions per second
✓ LastIndexOf	3,897,748 Ops/sec
Regex	1,440,913 Ops/sec
Regex loop	1,224,273 Ops/sec
LastIndexOf B	1,176,858 Ops/sec
Original	882,344 Ops/sec
Original reversed	811,113 Ops/sec
LastIndexOf 2	722,780 Ops/sec

Script Preparation code:

function getCookieIX_B(name, str,idx) {
  name = "; " + name + "=";
  var ck = str || document.cookie;
  ck = "; " + ck;
  if ((idx = ck.lastIndexOf(name)) == -1) {
    return undefined;
  }
  var nameLength = name.length;
  var p1 = ck.substring(idx + nameLength);
  var idx2 = p1.indexOf(";");
  idx2 = idx2==-1 ? undefined : idx2;
  var p2 = p1.substring(0, idx2);
  return decodeURIComponent(p2);
}
function getCookieIX(name,str){
  name = name+'=';
  var ck = str || document.cookie;
  var idx = ck.lastIndexOf(name);
  if(idx==-1){ return undefined}
  var nameLength = name.length;
  var p1 = ck.substring(idx+nameLength);
  var idx2 = p1.indexOf(';');
  if(idx2>-1){
    p1 = p1.substring(0,idx2);
  }
  return decodeURIComponent(p1);
}

function getCookieIX2(name, str,idx) {
  name = "; " + name + "=";
  var ck = str || document.cookie;
  ck = "; " + ck;
  if ((idx = ck.lastIndexOf(name)) == -1) {
    return undefined;
  }
  var nameLength = name.length;
  var p1 = ck.substring(idx + nameLength);
  p1 = p1.split(';')[0];
  return decodeURIComponent(p1);
}

function getCookie(name,str) {
  var nameEQ = name + "=";
  var ca = (str||document.cookie).split(";");
  for (var i = 0; i < ca.length; i++) {
    var c = ca[i];
    while (c.charAt(0) == " ") c = c.substring(1, c.length);
    if (c.indexOf(nameEQ) == 0) {
      var d = c.substring(nameEQ.length, c.length);
      d = decodeURIComponent(d);
      return d;
    }
  }
  return undefined;
}

function getCookieM(name,str) {
  name = name + "";
  var re = new RegExp("(^| )" + name + "=([^;]+)", "gmi");
  var m = (str||document.cookie).match(re);
  if (!!m) {
    m = m.pop();
    m = m.substring(m.indexOf("=") + 1);
    m = !!m ? decodeURIComponent(m) : m;
    return m;
  }
}

function getCookieW(name, str) {
  var str = str || document.cookie;
  var re = new RegExp("(?:^|; )("+name+"+?)(?:=([^;]*))?(?:;|$)", "gi");
  var value;
  var match;
  while ((match = re.exec(str))) {
    re.lastIndex = match.index + match.length - 1;
    var k = match[1];
    var v = decodeURIComponent(match[2]);
    !!v && (value = v);
  }

  return value;
}

function getCookieR(name,str) {
  var nameEQ = name + "=";
  var ca = (str||document.cookie).split(";");
  var cal = ca.length;
  for (var i = cal; i >= 0; i--) {
    var c = ca[i];
    if (!!c) {
      c = c.trim();
      if (c.indexOf(nameEQ) == 0) {
        var d = c.substring(nameEQ.length, c.length);
        d = decodeURIComponent(d);
        return d;
      }
    }
  }
  return undefined;
}
function generateTestData(){
  let foo = [];
  for (let i = 0; i < 20; i++) {
    var x = i+1;
    foo.push('foo_'+x+'='+'bar_'+x+'_'+performance.now());
    foo.push('foo_'+x+'='+'bar_second_'+x+'_'+performance.now());
  }
  foo = foo.join('; ');
  return foo;
}
var hay = generateTestData();

Run results for: Fetch cookie value

Regex loop

Regex

Original

Original reversed

LastIndexOf

LastIndexOf B

LastIndexOf 2