Run results for: object read vs write

Run details:

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_11_6) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/53.0.2785.101 Safari/537.36

Browser: Chrome 53

Operating system: Mac OS X 10.11.6

Device Platform: Other

Date tested: 7 years ago

Test name	Executions per second
write without reading	530.6 Ops/sec
check first before writing	507.6 Ops/sec

Script Preparation code:

var obj = {};
var arr = ['a', 'b', 'c', 'd'];

Tests:

write without reading
for (var i = 0; i < 10000; i++) { obj[arr[i % 4]] = true; }
check first before writing
var key; for (var i = 0; i < 10000; i++) { key = arr[i % 4]; if (!obj[key]) { obj[key] = true; } }