Tidy up equals snippet

snippets/equals.md

@@ -15,13 +15,18 @@ Performs a deep comparison between two values to determine if they are equivalen
 ```js
 const equals = (a, b) => {
   if (a === b) return true;
+
   if (a instanceof Date && b instanceof Date)
     return a.getTime() === b.getTime();
+
   if (!a || !b || (typeof a !== 'object' && typeof b !== 'object'))
     return a === b;
+
   if (a.prototype !== b.prototype) return false;
-  let keys = Object.keys(a);
+
+  const keys = Object.keys(a);
   if (keys.length !== Object.keys(b).length) return false;
+
   return keys.every(k => equals(a[k], b[k]));
 };
 ```