# Welcome to the Highcharts Maps JS (highmaps) Options Reference

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

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# chart.numberFormatter

Callback function to override the default function that formats all the numbers in the chart. Returns a string with the formatted number. Since v12.6.0, the callback also receives `ctx` as the last argument, so that arrow functions can access the same context as regular functions using `this`.