Converting IActionResult view to javascript file with custom ActionFilterAttribute in Asp.Net Core 2x

JavascriptOutputAttribute.cs

namespace yourApplicationNameSpace
{
    public class JavascriptOutputAttribute : ActionFilterAttribute
    {
        private static readonly Regex OpenScriptTag = new Regex(@"^\s*<script[^>]*>", RegexOptions.Compiled);
        private static readonly Regex CloseScriptTag = new Regex(@"</script>\s*$", RegexOptions.Compiled);

        public override async Task OnResultExecutionAsync(ResultExecutingContext context, ResultExecutionDelegate next)
        {
            var resp = context.HttpContext.Response;
            using (var buffer = new MemoryStream())
            {
                var realBody = resp.Body;
                context.HttpContext.Response.Body = buffer;
                context.HttpContext.Response.ContentType = "text/javascript";
                await next();
                var newResponse = ReformatResponseToJavascriptFile(buffer);
                using (var newResponseBuffer = new MemoryStream(Encoding.UTF8.GetBytes(newResponse)))
                {
                    resp.Body = realBody;
                    await newResponseBuffer.CopyToAsync(realBody);
                }
            }
        }


        private static string ReformatResponseToJavascriptFile(MemoryStream buffer)
        {
            string response;
            buffer.Seek(0, SeekOrigin.Begin);
            using (var sr = new StreamReader(buffer))
            {
                response = sr.ReadToEnd();
            }
            if (OpenScriptTag.IsMatch(response) && CloseScriptTag.IsMatch(response))
            {
                response = OpenScriptTag.Replace(response, string.Empty);
                response = CloseScriptTag.Replace(response, string.Empty);
            }
            return response;
        }

        
    }
}

how to use it:

[JavascriptOutput]
public IActionResult MyDynamicJavascriptFile()
{
return View();
}