array.length vs. cached

JavaScript performance comparison

Revision 10 of this test case created by

Preparation code 


      
      <script>

        Benchmark.prototype.setup = function() {

          
  var a = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9];
  a = a.concat(a, a, a, a, a, a, a, a);

        
  };


      
</script>

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Testing in CCBot 2.0.0 / Other 0.0.0
Test Ops/sec
not-cached 
(function(a) {
  var sum = 0;
  for (var i = 0; i < a.length; ++i) {
    sum += a[i];
  }
  return sum;
})(a);
 pending…
cached 
(function(a) {
  var sum = 0;
  for (var i = 0, aLen = a.length; i < aLen; ++i) {
    sum += a[i];
  }
  return sum;
})(a);
 pending…
cached, decrement 
(function(a) {
  var sum = 0;
  for (var i = a.length; i--;) {
    sum += a[i];
  }
  return sum;
})(a);
 pending…
cached, decrement 2 
(function(a) {
  var sum = 0;
  for (var i = a.length; --i;) {
    sum += a[i];
  }
  return sum;
})(a);
 pending…
cached, decrement, do while loop 
(function(a) {
  var i = a.length,
      sum = 0;
  do {
    sum += a[i];
  } while (i--);
  return sum;
})(a);
 pending…
cached, decrement, while loop 
(function(a) {
  var i = a.length,
      sum = 0;
  while (i--) {
    sum += a[i];
  }
  return sum;
})(a);
 pending…

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