in vs undefined

JavaScript performance comparison

Test case created by kitsonk

Preparation code

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

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Testing in unknown unknown
Test Ops/sec
in
if (!('children' in item)) {
  item.children = [];
}
pending…
undefined
if (!(item.children)) {
  item.children = [];
}
pending…

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