Ajax client test

salary_slip.js

cur_frm.cscript.employee = function(doc,dt,dn){
        return $c_obj(doc, 'get_emp_and_leave_details','',function(r, rt) {
            console.log("default====="); 
            var doc = locals[dt][dn];
            cur_frm.refresh(); // Once this called, the changes made using customize script are reverted 
            calculate_all(doc, dt, dn);
        });
}

salary_slip_custom.js

cur_frm.cscript.custom_employee = function(doc, dt, dn) {
    frappe.call({
        method:"frappe.client.get_value",
        args: {
            doctype: "Sales Person",
            fieldname: "name",
            filters: {employee: doc.employee}
        },
        callback: function(data) {
            // There is one sales person tied to this employee
            if (data.message)
            {
                console.log(data.message);
                cur_frm.set_value("sales_person", data.message.name);
            }
        }
    });
}