Preparation code

 
<script>
  Benchmark.prototype.setup = function() {
    var Cls = {
      _class: Boolean,
      fromURI1: function(uri) {
        var item = null;
        if (!item) return;
      },
      fromURI2: function(uri) {
        var item = null;
        if (!(item instanceof this._class)) return;
      }
    };
  };
</script>

Test runner

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Cls.fromURI1('hello');

Cls.fromURI2('hello');

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