Run results for: new Date(date) vs new Date(normalizeToLocalDate(date))

Run details:

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/127.0.0.0 Safari/537.36

Browser: Chrome 127

Operating system: Mac OS X 10.15.7

Device Platform: Desktop

Date tested: one year ago

Test name	Executions per second
new Date(dateTimeISO)	4275112.0 Ops/sec
new Date(normalizeToLocalDate(dateTimeISO))	3377427.8 Ops/sec
new Date(dateOnlyISO)	5799811.5 Ops/sec
new Date(normalizeToLocalDate(dateOnlyISO))	2309164.2 Ops/sec

Script Preparation code:

var dateTimeISO = '2024-08-21T17:00:00.000Z'
var dateOnlyISO = '2024-08-21'

var normalizeToLocalDate = (date) =>
    /^\s*\d{4}-\d{2}-\d{2}\s*$/.test(date) ? date.replace(/-/g, '/') : date;

Tests:

new Date(dateTimeISO)
new Date(dateTimeISO)
new Date(normalizeToLocalDate(dateTimeISO))
new Date(normalizeToLocalDate(dateTimeISO))
new Date(dateOnlyISO)
new Date(dateOnlyISO)
new Date(normalizeToLocalDate(dateOnlyISO))
new Date(normalizeToLocalDate(dateOnlyISO))

Run results for: new Date(date) vs new Date(normalizeToLocalDate(date))

new Date(dateTimeISO)

new Date(normalizeToLocalDate(dateTimeISO))

new Date(dateOnlyISO)

new Date(normalizeToLocalDate(dateOnlyISO))