Excel permits associating the text of the category axis with a Custom Angle (see attached image). I'm unable to determine the class or method to permit the same when creating a chart in the JavaScript Excel support. I am using 2019.1.
Thank you.
You would use the rotation method of the ticklabels of the axis.
chart.axisCollection($.ig.excel.AxisType.category).tickLabels().rotation(-45);