I am trying to create charts using Highcharts and Sharepoint Rest API. Essentially, I am using the code posted on Github here: https://github.com/Ramakrishnan-1/HighCharts-For-SharePoint-List-RESTAPI/blob/main/BuildHighCharts.js

The list I am using contains statuses of multiple tasks assigned to different users. It also contains a week column which is a calculated field.

It works fine to create a chart that distinguishes between Pending and Completed Items, but we would need a weekly overview of them, indicating how many items are Completed and Pending in each week. As a later addition, I would like to show only the trailing 4 or 8 weeks. The weeks that should be used are available in my Sharepoint list, and I am pulling that information using the Rest API. But I am getting stuck at counting these items for each week and then passing them over as data series to highcharts.

Has anyone experience with this and can give me a hint on how to realize it?