Refactor isOkVarChar function for simplicity and efficiency

Author: mic1on

Diff for: jQuery-hook.js

@@ -312,16 +312,7 @@
      * @returns {boolean}
      */
     function isOkVarChar(c) {
-        if (c >= 'a' && c <= 'z') {
-            return true;
-        }
-        if (c >= 'A' && c <= 'Z') {
-            return true;
-        }
-        if (c >= '0' && c <= '9') {
-            return true;
-        }
-        return false;
+        return (/^[a-zA-Z0-9]$/).test(c);
     }
 
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