When you export a page or pages some amount of Javascript is included in the page or referenced in an external javascript file.
This Javascript handles support for scaling a page up or down, switching between different artboards when a user clicks on a link, showing different artboards when the URL changes and for displaying pop ups as shown in an XD prototype.
Of course you can use your own Javascript and exclude the default by editing the HTML template.
Select the artboard that you use for exporting and open the HTML template and remove the line:
<—scripts—->
When you export the default Javascript and any custom will Artboard JS will be excluded.
You can still add JS through code snippets or by including references to your own files:
You can also use a code block: