JavaScript/유효성 체크(정규식)

// YYYYmmdd -> Date
function getValidDate(dtStr){
  let match = dtStr.trim().match(/^\d{8}$/);
  if (match == null) return false;
  
  let year = dtStr.substr(0, 4);
  let month = dtStr.substr(4, 2);
  let date = dtStr.substr(6, 2);
  return new Date(year+"-"+month+"-"+date);
}

// 10,000,000 -> 10000000
function getVaildNumber(str, start, end){
	let number = str.trim().replace(/,/g, '');
    let match = number.match(/^\d+$/);
    if (match == null) return false;
    if (start > number) return false;
    if (end < number) return false; 
    return number;
}