ibayazit

const number = 123456.789;

console.log(new Intl.NumberFormat('tr-TR', { style: 'currency', currency: 'TRY' }).format(number));
// expected output: "₺123.456,79"

// the Japanese yen doesn't use a minor unit
console.log(new Intl.NumberFormat('ja-JP', { style: 'currency', currency: 'JPY' }).format(number));
// expected output: "￥123,457"

// limit to three significant digits

ibayazit

visa
4[0-9]{12}(?:[0-9]{3})?
mastercard
^5[1-5][0-9]{14}
american express
^3[47][0-9]{13}
diners club
^3(?:0[0-5]|[68][0-9])[0-9]{11}
discover
^6(?:011|5[0-9]{2})[0-9]{12}

ibayazit

CSS : 
  @media (prefers-dark-interface) { 
    color: white; background: black 
  }


JS : 
  if (window.matchMedia && window.matchMedia('(prefers-color-scheme: dark)').matches) {
    // dark mode
  }