Is generating JS code which defines constants, considered bad practice?

I've seen things like this in many projects. Server generates html page with <script> tag, and JS code in it, which defines some constants, using templates.

For example.

<script>
  window.USER_ID = "<%= getUserId() %>";
  window.BASE_PATH = "<%= server.basePath %>";
</script>

Is this considered bad practice? If so, what's good way to pass server constants to client?