# 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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# xAxis.labels.formatter

Callback JavaScript function to format the label. The value is given by `this.value`. Additional properties for `this` are `axis`, `chart`, `isFirst`, `isLast` and `text` which holds the value of the default formatter. Since v12.6.0, the callback also receives `ctx` as the first argument, so that arrow functions can access the same context as regular functions using `this`.

Defaults to a built in function returning a formatted string depending on whether the axis is `category`, `datetime`, `numeric` or other.