Run results for: Intl.DateTimeFormat vs Reduce/Replace Format

Run details:

User agent: Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:86.0) Gecko/20100101 Firefox/86.0

Browser: Firefox 86

Operating system: Ubuntu

Device Platform: Desktop

Date tested: 3 years ago

Test name	Executions per second
Intl.DateTimeFormat	4857.4 Ops/sec
Reduce/Replace Format	317733.6 Ops/sec

Script Preparation code:

var date = new Date(2021, 2, 24)

var formatDateByIntlDateTimeFormat = (date) => {
  return new Intl.DateTimeFormat('pt-BR').format(date)
}

var tokens = {
  // Padded day       = 01, 02, ..., 31
  DD: (date) => date.getDate().toString().padStart(2, '0'),
  // Padded month     = 01, 02, ..., 12
  MM: (date) => (date.getMonth() + 1).toString().padStart(2, '0'),
  // Padded year      = 0001, 0002, ..., 1995, ..., 2020, 2021
  YYYY: (date) => date.getFullYear().toString().padStart(4, '0'),
};

var formatDateByReduceReplace = (date, format = 'DD/MM/YYYY') => {
  return Object.entries(tokens).reduce(
    (result, [pattern, fn]) => result.replace(new RegExp(pattern, 'g'), fn(date)),
    format
  );
};

Tests:

Intl.DateTimeFormat
formatDateByIntlDateTimeFormat(date)
Reduce/Replace Format
formatDateByReduceReplace(date, 'DD/MM/YYYY')