outputting javascript from a php script?

One short question: If I have a javascript script tag in a page that sets the src attribute to a php script Before I have the php script send the response via print or echo I have to call header('content-type: <?>'); so what would be the content type for javascript code? text/javascript or application-x/javascript or ? Apologies if this is considered off topic I have done this with css and used header('content-type text/css') Also I figured out how to get a self processing page to send a response to an ajax request sent to it by calling header('content-type:text/plain') for a plain text response. Thank you for time and attention JK