refactor(isFQDN): simplify function test cases and fix issue with numeric domain names

tux-tn · tux-tn · commit b35b1f8efed5 · 2020-12-04T13:22:25.000+01:00
diff --git a/src/lib/isFQDN.js b/src/lib/isFQDN.js
@@ -17,39 +17,52 @@ export default function isFQDN(str, options) {
     str = str.substring(0, str.length - 1);
   }
   const parts = str.split('.');
-  for (let i = 0; i < parts.length; i++) {
-    if (parts[i].length > 63) {
+  const tld = parts[parts.length - 1];
+
+  if (options.require_tld) {
+    // disallow fqdns without tld
+    if (parts.length < 2) {
       return false;
     }
-  }
-  if (options.require_tld) {
-    const tld = parts.pop();
-    if (!parts.length || !/^([a-z\u00a1-\uffff]{2,}|xn[a-z0-9-]{2,})$/i.test(tld)) {
+
+    if (!/^([a-z\u00a1-\uffff]{2,}|xn[a-z0-9-]{2,})$/i.test(tld)) {
       return false;
     }
+
     // disallow spaces && special characers
     if (/[\s\u2002-\u200B\u202F\u205F\u3000\uFEFF\uDB40\uDC20\u00A9\uFFFD]/.test(tld)) {
       return false;
     }
   }
-  for (let part, i = 0; i < parts.length; i++) {
-    part = parts[i];
-    if (!options.allow_numeric_tld && i === parts.length - 1 && /^\d+$/.test(part)) {
-      return false; // reject numeric TLDs
+
+  // reject numeric TLDs
+  if (!options.allow_numeric_tld && /^\d+$/.test(tld)) {
+    return false;
+  }
+
+  return parts.every((part) => {
+    if (part.length > 63) {
+      return false;
     }
+
     if (!/^[a-z_\u00a1-\uffff0-9-]+$/i.test(part)) {
       return false;
     }
+
     // disallow full-width chars
     if (/[\uff01-\uff5e]/.test(part)) {
       return false;
     }
-    if (part[0] === '-' || part[part.length - 1] === '-') {
+
+    // disallow parts starting or ending with hyphen
+    if (/^-|-$/.test(part)) {
       return false;
     }
+
     if (!options.allow_underscores && /_/.test(part)) {
       return false;
     }
-  }
-  return true;
+
+    return true;
+  });
 }
