This sample demonstrates rendering HeatMap control by providing desired data from a pivot table on selection. Not only HeatMap, but any other control (including third party) can be used for this purpose.
In this sample, the cell selection feature is enabled with the api allowSelection property and its type and mode are configured using the selectionSettings property. The cellSelected event gets fired on every selection operation performed in the pivot table. This event returns the selected cell information, like row header name, column header name, measure name, and value. Based on this information, the heatmap will be plotted. More information on the Essential JS2 Pivot Table & Heatmap can be found in these Selection & Heatmap documentation section.