performance - Does JavaScript cache/optimize code if repeated multiple times? -

i'm writing small framework test speed of javascript functions. when repeatedly call same methods same parameter, gives me strange results:

function           execution time  isevenbitwise      38.00000000046566 isevenmodulo       38.00000000046566 isevenpointless    38.00000000046566 

here functions:

var myfunctions =  {     isevenbitwise: function(number)      {         return !(number & 1);       },     isevenmodulo: function(number)     {         return (number % 2 == 0);     },     isevenpointless: function(number)     {         return 1;     } } 

the code runs functions:

performancetest.prototype.measuretime = function() {     (var indextests = 0; indextests < this.testcount; indextests++)     {         var results = [];          (var currentfunction in this.functions) {             var contextfunction = this.functions[currentfunction];              var starttime = performance.now();             (var = 0; < this.iterationspertest; i++)             {                 var heh = contextfunction.apply(this, arguments)             }             var executiontime = performance.now() - starttime;              var result = {};             result.testname = currentfunction;             result.executiontime = executiontime;             results.push(result);         }          this.testresults.push(results);     } } 

does javascript interpreter cache/optimize code? if so, how work? or there else happening i'm not aware of?

edit: seems occur in chrome, firefox works fine these results:

function           execution time  isevenbitwise      9.652258097220447 isevenmodulo       37.546061799704376 isevenpointless    8.512472488871936 

after looking @ code going make guess chrome being smart doing. seeing this:

 var starttime = performance.now();  (var = 0; < this.iterationspertest; i++)  {       var heh = contextfunction.apply(this, arguments)  } var executiontime = performance.now() - starttime; 

it correctly assessing contextfunction has no side effects, recognising heh variable exists within loop scope , never used , optimising entire loop away because doesn't anything.