Mastering D3 CH2 2.2 BARCODE CHART - part 2 v3 examples here: http://hanmomhanda.github.io/mastering-d3-html/chapter02/02-barcode-chart/ Problem in converting from v3 to v5 and looks like book has poor practice of d3.js (https://stackoverflow.com/questions/45181773/d3-js-raw-selection-get-error-uncaught-typeerror-cannot-read-property-0-of-u)