On Listings 4.8 and 4.9, it talks about exporting an "addTwo" function that takes a number and adds two to it. In Listing 4.9, the code passes the number 4 as an argument to the function, but the comment immediately after says it returns 4. It should return 6:
4.8 (basicmath.js):
exports.addTwo = n => n+2;
4.9:
const basicMath = require('./basicmath');
basicMath.addTwo(4); // returns 4
4.9 should be:
const basicMath = require('./basicmath');
basicMath.addTwo(4); // returns 6
