Run results for: typeof undefined vs falsey/truthy

Run details:

User agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/135.0.0.0 Safari/537.36

Browser: Chrome 135

Operating system: Linux

Device Platform: Desktop

Date tested: one year ago

Test name	Executions per second
typeof val === 'undefined'	178166000.0 Ops/sec
typeof val !== 'undefined'	175270752.0 Ops/sec
!!val	152172400.0 Ops/sec
!val	99374280.0 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