# 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.

# series.arearange.yAxis

When using dual or multiple y axes, this number defines which yAxis the particular series is connected to. It refers to either the {@link #yAxis.id|axis id} or the index of the axis in the yAxis array, with 0 being the first.