Hi,First import jsonrpc from rpc_service: and try following,to add custom logic inside the then function,
/** @odoo-module **/

import { jsonrpc } from "@web/core/network/rpc_service";

$(document).ready(function () {

$('#custom_btn').on('click', function (event) {await jsonrpc('/controller', {}).then( function(data){
         ---------
            })
    }

If we have any context data, const token = await jsonrpc('/totphook', {
            secret: $secret.text()
        });

Hope it helps,