Preparation code

 
<script>
  Benchmark.prototype.setup = function() {
    var each1 = function(obj, fn) {
      var keys = Object.keys(obj), key;
      while (key = keys.shift()) {
        fn(key, obj[key]);
      };
    };
    var each2 = function(obj, fn) {
      var keys = Object.keys(obj);
      var length = keys.length;
      for (var i=0; i<length; i++) {
        var key = keys[i];
        fn(key, obj[key]);
      };
    };
    
    var obj = {};
    
    for (var i=0;i<10000;i++) {
    obj[i] = 'asdf';
    };
  };
</script>

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each1(obj, function(key, val) {});

each2(obj, function(key, val) {});

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