I have access to an old private website, as a client.

The original TeX command is not present anywhere in the page_source nor the rendered document. However, it is clearly somewhere in memory, because I can right click on the math expression, select “Show Math as TeX command”, and see the original TeX command.

How can I retrieve the original command in javascript, from the browser console?

I tried to do:

window.MathJax.startup.document.getMathItemsWithin(document.body);

but this returns an empty list, even though the document body is full of mathematical expression.