How to access the JavaScript variable in the python code in Web2py's view

Question

I'm trying to store the value of the drop-down 'product' in a javaScript variable and then trying to use that variable in Python code in html view of Web2py framework to further create the drop down for the other component. I tried two different ways, but both of them did not work. I want to do a query on database using a keyword which is selected from the Product drop-down and hence generating the second drop down.

<script>
        function run()
        {
            var e = document.getElementById('local_product');
            var strUser = e.options[e.selectedIndex].text;
            document.getElementById('div_release').innerHTML =' <label>Release : </label> {{rows1 = db(db.Builds.Build.like(\"}}strUser%{{\"")).select()}} <select> {{for r1 in rows1:}}<option>{{=r1.Build}}</option> {{pass}}</select>'


    or
        document.getElementById('div_release').innerHTML =' <label>Release: </label> {{rows2=db.executesql("Select Build from Builds where Build like\"request.vars.prod_tab\"" )}} <select> {{for r1 in rows2:}}<option>{{=r1}}</option> {{pass}}</select>'

 }

</script>
<form method="POST" action="" name="product_filter">
<label>Product: </label>
<select id="local_product" onchange="run()" name=prod_tab >
{{ for r in product_list: }}
<option value="{{r}}">
{{=r}}
</option>
{{pass}}
</select>
{{pass}}
<input type="Submit" name=Set Value="Set">
<form>

Answer 1

Python code in web2py views is executed on the server before the page is sent to the browser, so it is not possible to execute any Python code within the browser in response to user actions. Instead, you must send an Ajax request to the server to retrieve additional data to inject in the page. For ideas on how to achieve what you want, see this answer.