How to give a warning for Non-JavaScript Browsers?

To let users know about non-JavaScript web browsers, use the <noscript> tag. The HTML <noscript> tag is used to handle the browsers, which do recognize <script> tag but do not support scripting. This tag is used to display alternate text message

Here’s an example,

<!DOCTYPE html>
      <title>HTML noscript Tag</title>

            document.write("Hello JavaScript!")

         Your browser does not support JavaScript!