IP4 validation

validateIp.ts

// Using Loops (and Regex)

const validateIP = ip => {
  const regex = /^\d+$/;
  const s = IP.split('.');
  if(s.length !== 4) return false;

  for(let i = 0; i < s.length; i++) {
    if(!regex.test(s[i])) return false;
    if(s[i].length > 1 && s[i].startsWith('0')) return false;

    const n = parseInt(s[i]);
    if(Number.isNaN(n)) return false;

    if(n < 0 || n > 255) return false;
  }
  return 'IPv4';
}
    
    
// Using a filter and map
const validRange = (n: number): boolean => n >= 0 && n <= 255;

const validateIP = (ip: string): boolean => {
  const numbers: string[] = ip.split('.');
  return numbers.length === 4
    && numbers
      .filter((x) => Number(x).toString() === x) // remove any numbers with leading 0s
      .map((x) => parseInt(x, 10)) // convert to number
      .filter(validRange) // filter out invalid range
      .length === 4; // check we still have 4 numbers
};