# Welcome to the Highcharts Gantt JS (gantt) Options Reference

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

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# navigator.xAxis.events.setExtremes

Fires when the minimum and maximum is set for the axis, either by calling the `.setExtremes()` method or by selecting an area in the chart. One parameter, `event`, is passed to the function, containing common event information.

The new user set minimum and maximum values can be found by `event.min` and `event.max`. These reflect the axis minimum and maximum in data values. When an axis is zoomed all the way out from the "Reset zoom" button, `event.min` and `event.max` are null, and the new extremes are set based on `this.dataMin` and `this.dataMax`.