Run results for: object property lookup: in operator vs undefined comparison

Run details:

User agent: Mozilla/5.0 (compatible; MSIE 9.0; Windows NT 6.1; Win64; x64; Trident/5.0)

Browser: IE 9

Operating system: Windows 7

Device Platform: Desktop

Date tested: 3 years ago

Test name	Executions per second
in operator	3697787.5 Ops/sec
!==undefined comparison	4292126.0 Ops/sec

Script Preparation code:

var obj={prop:'dddd'};

Tests: