const books = {
"1": [["foo", 5], ["bar", 8], ["noo", 9]],
"2": [["bmk", 7]],
"7": [["jol", 1], ["lon", 2]]}
const values = Object.values(obj);const count = values.flat().length;
// или
const count = [].concat(...values).length;
// или
const count = values.reduce((acc, n) => acc + n.length, 0);
// или
const count = eval(values.map(n => n.length).join('+')) || 0;
const books = {
"1": [["foo", 5], ["bar", 8], ["noo", 9]],
"2": [["bmk", 7]],
"7": [["jol", 1], ["lon", 2]]
}
let count;
for (const key in books) {
if (typeof books[key] == 'object') {
count += books[key].length
console.log(count)
}
}