Get the HTTP Basic Auth username from javascript?

I have a webpage that is only accessible over http basic auth. How can I figure out the basic auth username in javascript in that page. i.e. when someone visits it (after logging in),开发者_开发问答 I want to make a popup that says "Hello, you're currently signed in as the user $USERNAME"

It's not possible purely from JavaScript. You'd have to have the server side script pick up the username from the request, and insert it in the generated page code for the script to pick up. (eg. <script type="text/javascript">var username=(insert JSON-encoded string here);</script>.

javascript:window.alert(document.location) seems to give a URL with a username (but no password). This may not be true in other browsers.