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

new Date(dateOnlyISO)

5.8M/s

new Date(dateTimeISO)

4.3M/s

new Date(normalizeToLocalDate(dateTimeISO))

3.4M/s

new Date(normalizeToLocalDate(dateOnlyISO))

2.3M/s

View exact numbers

Test name	Executions per second
✓ new Date(dateOnlyISO)	5,799,812 Ops/sec
new Date(dateTimeISO)	4,275,112 Ops/sec
new Date(normalizeToLocalDate(dateTimeISO))	3,377,428 Ops/sec
new Date(normalizeToLocalDate(dateOnlyISO))	2,309,164 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))