JSFiddle - React, Tailwind, and code Playground

JavaScript

var count = 100000000;
var res1, res2, res3, res4;
    
(function (d) {
    var a;
    for (var i=0; i<count; i++) {
      a = a + 1;
    }
    res1 = +new Date() - d;
})(+new Date());

(function (d) {
    var a, i;
    for (i=0; i<count; i++) {
      a = a + 1;
    }
    res2 = +new Date() - d;
})(+new Date());
     
(function (d) {
    for (var i=0; i<count; i++) {
      var a = a + 1;
    }
    res3 = +new Date() - d;
})(+new Date());

(function (d) {
    for (var i=0, a = 0; i < count; i++) {
      a = a + 1;
    }
    res4 = +new Date() - d;
})(+new Date());
        
        document.body.innerHTML = "res1: "+ res1 + "<br/>" + "res2: "+ res2 + "<br/>" + "res3: "+ res3 + "<br/>" + "res4: "+ res4 + "<br/>";