in vs == undefined

JavaScript performance comparison

Revision 2 of this test case created by Jelle De Loecker

Preparation code

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

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Testing in unknown unknown
Test Ops/sec
in
if('key' in object) {};
pending…
typeof != undefined
if(typeof object.key != 'undefined') {};
pending…
!== undefined
if (object.key !== undefined) {};
pending…
!== undefined (array like)
if (object['key'] !== undefined) {};
pending…

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