How to get data from series item contributors for usage in a function like yAxis.stackLabels.formatter

Issue Description

A customer wants to use values from series item contributors in the highcharts api function yAxis.stackLabels.formatter. https://api.highcharts.com/highcharts/yAxis.stackLabels.formatter

Their attempts fail for anything other than totals, like: function() {return this.total;}

Resolution

Within the highcharts object the data model is complex due to the "stacking". So you need to iterate thru the individual items of the objects in our function. For example, if  fruit is setup as the series contributor like:

Then a function could be:

<![CDATA["function() {var list = '', x = this.x, series = this.axis.chart.options.series, s; for (s = 0; s < series.length; ++s) if (series[s].data[x].y != null) list += series[s].data[x].fruit + ' '; return list;}"]]>

Ref. Case 01525594