JAVASCRIPT
Validating IPv4 Addresses with Regex
Validate IPv4 addresses with a precise JavaScript regex. Ideal for web forms and data processing, ensuring adherence to the standard dotted-decimal notation (0.0.0.0 to 255.255.255.255).
function isValidIPv4Address(ip) {
// Regex for IPv4 address validation
// Matches numbers 0-255 separated by dots.
const ipv4Regex = /^(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)$/;
return ipv4Regex.test(ip);
}
console.log("Valid IP:", isValidIPv4Address("192.168.1.1")); // true
console.log("Valid IP:", isValidIPv4Address("0.0.0.0")); // true
console.log("Valid IP:", isValidIPv4Address("255.255.255.255")); // true
console.log("Invalid IP (too high):";, isValidIPv4Address("256.0.0.0")); // false
console.log("Invalid IP (missing segment):";, isValidIPv4Address("192.168.1")); // false
console.log("Invalid IP (text):";, isValidIPv4Address("abc.def.ghi.jkl")); // false
How it works: This JavaScript function utilizes a regular expression to validate if a given string is a correctly formatted IPv4 address. The pattern `(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)` is a non-capturing group that matches any number from 0 to 255. This group is repeated exactly three times, followed by a literal dot `\.`, and then the same pattern for the final segment. The `^` and `$` anchors ensure the entire string must match the pattern.