Run results for: typeof undefined vs falsey/truthy

Run details:

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/129.0.0.0 Safari/537.36

Browser: Chrome 129

Operating system: Mac OS X 10.15.7

Device Platform: Desktop

Date tested: one month ago

Test name	Executions per second
typeof val === 'undefined'	9744942.0 Ops/sec
typeof val !== 'undefined'	9913581.0 Ops/sec
!!val	10258979.0 Ops/sec
!val	10022835.0 Ops/sec

Script Preparation code:

const undef = undefined
function checkIsUndefined(val) {
  return typeof val === 'undefined'
}
function checkIsNotUndefined(val) {
  return typeof val !== 'undefined'
}
function checkIsTruthy(val) {
  return !!val
}
function checkIfFalsey(val) {
  return !val
}

Tests:

typeof val === 'undefined'
checkIsUndefined(undef)
typeof val !== 'undefined'
checkIsNotUndefined(undef)
!!val
checkIsTruthy(undef)
!val
checkIfFalsey(undef)

Run results for: typeof undefined vs falsey/truthy

which is faster

typeof val === 'undefined'

typeof val !== 'undefined'

!!val

!val