Run results for: is variable undefined? typeof variable === "undefined" vs variable === undefined

Run details:

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/94.0.4606.85 YaBrowser/21.11.0.2054 Yowser/2.5 Safari/537.36

Browser: Yandex Browser 21

Operating system: Mac OS X 10.15.7

Device Platform: Desktop

Date tested: 3 years ago

Test name	Executions per second
typeof string is undefined	936976256.0 Ops/sec
typeof undefined is undefined	7946842.0 Ops/sec
string is undefined	7928349.0 Ops/sec
undefined is undefined	3934377.0 Ops/sec

Tests:

typeof string is undefined
typeof "not undefined" === "undefined"
typeof undefined is undefined
typeof undefined === "undefined"
string is undefined
"not undefined" === undefined
undefined is undefined
undefined === undefined

Run results for: is variable undefined? typeof variable === "undefined" vs variable === undefined

Comparing whether checking is (typeof variable === "undefined") is faster than (variable === undefined)

typeof string is undefined

typeof undefined is undefined

string is undefined

undefined is undefined