AJAX call using CustomJS

flask_bokeh_ajax.py

    data = {'x': ["0-7 days", "7-30 days", "31-90 days", ">90 days"],
            'All dogs': [41.4391, 34.8107, 15.6709, 4.4533],
            'Filtered': [0, 0, 0, 0]}
    source = ColumnDataSource(data=data)
    callback = CustomJS(args=dict(source=source), code="""
                $.ajax({
                    url: '/_ajax',
                    data: $("#filter_form").serialize(),
                    type: 'GET',
                    success: function(response) {
                        console.log(response);
                    var response_data = response;
                    var data = source.data;
                    data['Filtered'] = response_data['y_vals'];
                    source.change.emit();
                    var resultCount = "Your query returned " +  response_data['n_records'].toString() + " results.";
                    document.getElementById("n_results").innerHTML =   resultCount;
    },
                    error: function(error) {
                        console.log(error);
                    }
                });
                        """)