# JS API Reference

# Welcome to the Highcharts JS Options Reference

These pages outline the chart configuration options, and the methods and properties of Highcharts objects.

Feel free to search this API through the search bar or the navigation tree in the sidebar.

# chart.events.drilldown

Fires when a drilldown point is clicked, before the new series is added. This event is also utilized for async drilldown, where the seriesOptions are not added by option, but rather loaded async. Note that when clicking a category label to trigger multiple series drilldown, one `drilldown` event is triggered per point in the category.

Event arguments:

- `category`: If a category label was clicked, which index.

- `originalEvent`: The original browser event (usually click) that triggered the drilldown.

- `point`: The originating point.

- `points`: If a category label was clicked, this array holds all points corresponing to the category.

- `seriesOptions`: Options for the new series.