You can call Js functions as a script registered on the codebehind itself.
Page.RegisterStartupScript("key","value")
key is the name you want to give the script eg. "PageClose"
value is the;
stringBuilder str = new StringBuilder()
str.Append("<script = language='javascript'>");
str.Append("window.close();");
str.Append("</script>")
here instead of using the window.close you coud append your js function as a string, ideally i put this string builder class and build the script in the constructor if i need it always in the page
Then use this in the event handler you want to execute the script
Page.RegisterStartUp("PageClose",str.ToString());
This would place the javascript before the closing tag of the page thats rendered
Page.ClientScriptBlock("PageClose",str.ToString());
This would place the JS function after the opening tag of the page thats rendered
Hope this helps