JAVASCRIPT
Validate an IPv4 Address
Learn how to use a regular expression in JavaScript to accurately validate if a given string represents a valid IPv4 address, ensuring correct octet ranges.
function isValidIPv4(ip) {
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(isValidIPv4("192.168.1.1")); // true
console.log(isValidIPv4("255.255.255.255")); // true
console.log(isValidIPv4("10.0.0.0")); // true
console.log(isValidIPv4("192.168.1.256")); // false (invalid segment)
console.log(isValidIPv4("abc.def.ghi.jkl")); // false
console.log(isValidIPv4("123.45.67.890")); // false
How it works: This JavaScript function `isValidIPv4` employs a robust regular expression to determine if a string conforms to the standard IPv4 address format. The regex breaks down into four identical segments separated by dots, where each segment matches numbers from 0 to 255. This ensures that each octet is a valid number, preventing addresses like `192.168.1.256` from passing validation.