Preparation code

 
<script>
  Benchmark.prototype.setup = function() {
    var obj = Object.create(null, {
        foo : {
            get : function() {
                return 'value';
            }
        }
    });
    
    var propName = 'bar';
      
    
  };
</script>

Test runner

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if (propName in obj) {}

if (obj.bar === undefined) {}

if (typeof obj.bar === "undefined") {}

if (obj[propName] === undefined) {}

if (typeof obj[propName] === "undefined") {}

if (obj.bar) {} // caution: false negatives for 'false-y' values

if (obj[propName]) {} // caution: false negatives for 'false-y' values

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