I am using ExcelJS to read in an xlsx file. I need to read all of the columns of the xlsx, but I can't find anything about this in the documentation

I have something like this -

window.workbook = workbook;
const worksheet = workbook.getWorksheet("Input");
const idCol = worksheet.getColumn(1);
const nameCol = worksheet.getColumn(2);

I need to be able to iterate through all of the columns and add them to an array. I cant even find how to get the number of total columns...