typeof vs undefined vs void(0) check

JavaScript performance comparison

Revision 3 of this test case created by Jay Phelps

Preparation code

 
<script>
Benchmark.prototype.setup = function() {
    var x;
};
</script>

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Testing in unknown unknown
Test Ops/sec
typeof x === "undefined"
typeof x === "undefined"
pending…
x === undefined
x === undefined
pending…
x === void 0
x === void 0
pending…

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