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@@ -10,4 +10,12 @@ Inside Windows, there has been a full foundation for writing apps based on scrip
 
 Recently, I took out this function and saw various attempts to develop a system app, and based on this, I started the WelsonJS project.
 
-I wish you all the best. Thank you.
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+I wish you all the best. Thank you.
+
+### Technical limitation
+
+The specifications of the JavaScript engine built into Windows are intermediate between ECMAScript versions 3 and 4. We are using a polyfill library to raise this to ES5 and ES6 levels, but there are a few unsupported keywords.
+
+We know about Chakracore, known as an improved version of JScript, but it cannot be used in projects with web-based GUI because it has not integrated with HTML rendering engines (e.g., MSHTML, EdgeHTML).
+
+However, it will be included in future work because it is highly utilized for special purposes.