Convert Timestamp to Readable Date

/*
@okjson.schemaVersion 1
@okjson.name Convert Timestamp
@okjson.description Convert Unix timestamp to human-readable date.
@okjson.icon clock
@okjson.preprocessInput no
@okjson.openResultInNewWindow no
@okjson.author OK JSON
@okjson.authorURL https://okjson.app
*/
 
$include('dayjs.min');
 
function main(timestamp) {
  const number = parseFloat(timestamp);
  if (isNaN(number)) {
    $alert.error(
      'Input Error',
      `“${timestamp}” cannot be converted to number.`
    );
    return '';
  }
  let dayjsObject = null;
  if (timestamp.length === 10) {
    dayjsObject = dayjs.unix(number);
  } else if (timestamp.length === 13) {
    dayjsObject = dayjs(number);
  } else {
    $alert.error('Input Error', `“${timestamp}” is not a valid timestamp.`);
    return '';
  }
  const formatted = dayjsObject.format('YYYY-MM-DD HH:mm:ss');
  $alert.success(`Timestamp: ${timestamp}`, formatted);
  return '';
}