How to access plain text content retrieved via <script type="text/plain" src=...> in JavaScript?

When using <script type="text/plain" src="http://..."></script>, where the URL refers to a plain text file, is there a way to access the content of the file in JavaScript? The file is transferred to the browser, but the value of innerHTML property of the script element is not changed (it remains the empty string). Inspecting the element node in the DOM does not seem to reveal any property through which the content received could be found.

I know that XMLHTTPRequest can be used instead, but I’m interested in the problem why browsers fetch data in the way I described but do not seem to offer any access to it.