get_last_series_id.js

cur_frm.cscript.item_prefix = function() {
  // will be called on change of item_prefix
  
  // note: it is important to specifiy tablename.fieldname
  // in query as permissions are evaluated on this basis
  // and sql keywords must be in CAPS
  wn.call({
    method: "webnotes.widgets.query_builder.runquery", 
    args: {
        "query":"SELECT `tabItem`.name \
          FROM `tabItem` WHERE `tabItem`.name like '" + doc.item_prefix +"%' \
          ORDER BY name desc limit 1"
        }, 
    callback: function(r) { 
      // returned last value
      last_id = r.values[0][0]
    
      var new_id = /* some id logic */
    
      cur_frm.set_value("item_code", new_id);
    }
  });
}