To Validate the Filetype

This code will help to find file type, While upload the file and validate client on side

function validate1()
{
var File_Attach = document.getElementById("<%=File_Attach.ClientID%>").value;

if(File_Attach != "")
{
 if((File_Attach.indexOf(".pdf") > 0) || (File_Attach.indexOf(".xls") > 0) || (File_Attach.indexOf(".zip") > 0) || (File_Attach.indexOf(".rar") > 0))
                    {
	                    return true;
                    }	
                    else
                    {
	                    alert("only pdf,Excel,Zip,Winrar files are allowed");
	                    return false;
                    }	
}
}