The Nullish Coalescing Operator (??)
6.1
There are objects in the books array that don't have the onlineContent property at all. Loop over the books array, and log a string to the console in this format: "${title}" provides no data about its online content.
for (let i = 0; i < books.length; i++) {
books[i].onlineContent ?? console.log(`"${books[i].title} provides no data about its online content"`);
}