Index: compile_rules_js_convert.py
==================================================================
--- compile_rules_js_convert.py
+++ compile_rules_js_convert.py
@@ -32,10 +32,11 @@
     sCode = sCode.replace(".upper", ".toUpperCase")
     sCode = sCode.replace(".isdigit", ".gl_isDigit")
     sCode = sCode.replace(".isupper", ".gl_isUpperCase")
     sCode = sCode.replace(".islower", ".gl_isLowerCase")
     sCode = sCode.replace(".istitle", ".gl_isTitle")
+    sCode = sCode.replace(".isalpha", ".gl_isAlpha")
     sCode = sCode.replace(".capitalize", ".gl_toCapitalize")
     sCode = sCode.replace(".strip", ".gl_trim")
     sCode = sCode.replace(".lstrip", ".gl_trimLeft")
     sCode = sCode.replace(".rstrip", ".gl_trimRight")
     sCode = sCode.replace('.replace("."', r".replace(/\./g")

Index: js_extension/string.js
==================================================================
--- js_extension/string.js
+++ js_extension/string.js
@@ -18,10 +18,13 @@
         return nOccur;
     };
     String.prototype.gl_isDigit = function () {
         return (this.search(/^[0-9⁰¹²³⁴⁵⁶⁷⁸⁹]+$/) !== -1);
     };
+    String.prototype.gl_isAlpha = function () {
+        return (this.search(/^[a-zA-Zà-öÀ-Öø-ÿØ-ßĀ-ʯ]+$/) !== -1);
+    };
     String.prototype.gl_isLowerCase = function () {
         return (this.search(/^[a-zà-öø-ÿ0-9-]+$/) !== -1);
     };
     String.prototype.gl_isUpperCase = function () {
         return (this.search(/^[A-ZÀ-ÖØ-ߌ0-9-]+$/) !== -1);