दिन 23: असली Validation के लिए Regular Expressions

const pin = /^[1-9][0-9]{5}$/;     // Indian PIN code
console.log(pin.test('302003'));   // true
console.log(pin.test('012345'));   // false – cannot start with 0
console.log(pin.test('30200'));    // false – only 5 digits
console.log(pin.test('302003a'));  // false – $ means the string must end here

const patterns = {
  mobile: /^(?:\+?91[\s-]?|0)?[6-9]\d{4}[\s-]?\d{5}$/,              // +91 98290-12345, 09829012345 …
  pin:    /^[1-9]\d{5}$/,
  gstin:  /^\d{2}[A-Z]{5}\d{4}[A-Z][1-9A-Z]Z[0-9A-Z]$/,               // 15 chars: state code + PAN + entity + Z + checksum
  pan:    /^[A-Z]{5}\d{4}[A-Z]$/,
  ifsc:   /^[A-Z]{4}0[A-Z0-9]{6}$/,
  vehicle:/^[A-Z]{2}[ -]?\d{1,2}[ -]?[A-Z]{1,3}[ -]?\d{4}$/,           // RJ 14 CX 1234
};
const tests = {
  mobile: ['+91 98290-12345', '09829012345', '9829012345', '5829012345', '98290123'],
  pin: ['302003', '102003', '002003'],
  gstin: ['08ABCDE1234F1Z5', '08ABCDE1234F1X5'],
  pan: ['ABCDE1234F', 'ABCD1234F'],
  ifsc: ['SBIN0001234', 'SBIN1001234'],
  vehicle: ['RJ 14 CX 1234', 'RJ14CX1234', 'R 14 CX 1234'],
};
for (const [name, values] of Object.entries(tests)) {
  console.log(name.padEnd(8), values.map(v => `${v} ${patterns[name].test(v) ? '✅' : '❌'}`).join('  '));
}

function normaliseMobile(input) {
  const digits = input.replace(/\D/g, '');          // remove everything that is not a digit
  const ten = digits.replace(/^(91|0)(?=\d{10}$)/, '');   // drop a leading 91 or 0 if 10 digits remain
  return /^[6-9]\d{9}$/.test(ten) ? ten : null;
}
['+91 98290-12345', '(0) 98290 12345', '919829012345', '12345'].forEach(v => console.log(v.padEnd(18), '→', normaliseMobile(v)));

const pretty = n => n.replace(/^(\d{5})(\d{5})$/, '+91 $1 $2');    // $1, $2 = captured groups
console.log(pretty('9829012345'));

const sms = 'Order #1042 for ₹1,800 confirmed. Order #1043 for ₹650 pending. Call 98290 12345.';

console.log(/order #\d+/i.test(sms));                      // i = case-insensitive
console.log(sms.match(/#\d+/g));                           // g = all matches
for (const m of sms.matchAll(/#(?<id>\d+) for ₹(?<amount>[\d,]+) (?<status>\w+)/g)) {
  const { id, amount, status } = m.groups;                  // named groups
  console.log(id, Number(amount.replace(/,/g, '')), status);
}
console.log(sms.replace(/\d{5} \d{5}/, '***** *****'));   // mask a phone number
console.log('kaju  katli   box'.replace(/\s+/g, ' '));      // collapse spaces
console.log('Ghewar,Rasmalai; Ladoo | Peda'.split(/\s*[,;|]\s*/));

<input id="q" value="ka" placeholder="Search" aria-label="Search">
<ul id="list"></ul>

<script>
const items = ['Kaju Katli', 'Kalakand', 'Malai Ghewar', 'Besan Ladoo', 'Soan Papdi (1+1 offer)'];
const escape = s => s.replace(/[.*+?^${}()|[\]\\]/g, '\\$&');      // treat user text literally

function render() {
  const q = document.querySelector('#q').value.trim();
  const list = document.querySelector('#list');
  list.innerHTML = '';
  const re = q ? new RegExp(`(${escape(q)})`, 'gi') : null;
  for (const name of items) {
    if (re && !name.match(re)) continue;
    const li = document.createElement('li');
    if (!re) { li.textContent = name; list.append(li); continue; }
    name.split(re).forEach((part, i) => {               // split keeps captured groups
      const node = i % 2 ? document.createElement('mark') : document.createTextNode(part);
      if (i % 2) node.textContent = part;
      li.append(node);
    });
    list.append(li);
  }
}
document.querySelector('#q').addEventListener('input', render);
render();
</script>