Refactor: Simplified code by using \b in IPv4 regular expression

Closes validatorjs#1962

src/lib/isIP.js

@@ -30,7 +30,7 @@ import assertString from './util/assertString';
  * * */
 const IPv4SegmentFormat = '(?:[0-9]|[1-9][0-9]|1[0-9][0-9]|2[0-4][0-9]|25[0-5])';
 const IPv4AddressFormat = `(${IPv4SegmentFormat}[.]){3}${IPv4SegmentFormat}`;
-const IPv4AddressRegExp = new RegExp(`^${IPv4AddressFormat}$`);
+const IPv4AddressRegExp = new RegExp(`^\b${IPv4AddressFormat}\b$`);
 
 const IPv6SegmentFormat = '(?:[0-9a-fA-F]{1,4})';
 const IPv6AddressRegExp = new RegExp('^(' +
@@ -51,11 +51,7 @@ export default function isIP(str, version = '') {
     return isIP(str, 4) || isIP(str, 6);
   }
   if (version === '4') {
-    if (!IPv4AddressRegExp.test(str)) {
-      return false;
-    }
-    const parts = str.split('.').sort((a, b) => a - b);
-    return parts[3] <= 255;
+    return !!IPv4AddressRegExp.test(str);
   }
   if (version === '6') {
     return !!IPv6AddressRegExp.test(str);