I am also trying to find a solution for this, can anyone help ?

In the Odoo Studio : studio_customization where you add the <xpath> elements, inside /t or /t/t
 (<xpath expr="/t/t" position="inside">)
you can ad a script tag just as in html
<script>

//Javascript code

</script>
You can access the DOM and do many other things this way

guys, did you solve this? if not, you go like this:

<t t-jquery="[t-set*='columns_count']" t-operation="replace">
          <t t-js="ctx">
              var table = document.getElementById("tableId");
                        alert(table.offsetHeight);          
</t>
          <t t-if="show_order_numbers">
</t>
I have put t-jquery just that you know that t-js must go in there, but the value of t-jquery depends where you want to insert your js code.....

Same issue, did anyone manage to solve this ?