mongoose queries execution order - node.js

Question

I'm having a problem in My code using nodejs and mongoose. where I have a function that is supposed to get books from mongodb ( book.findOne) then update them using second query (updateMany).
the problem is that UpdateMany query executes before getting the books ..so my array stays empty and nothing is updated.
I know that node.js is asynchronous but how could i solve this ?
function UpdateBulk(completeValidBooks){
var existingRowsInDb = [];
completeValidBooks.forEach(function(currentBook) {
book.findOne({'ISIN': currentBook.ISIN },
function(error, result) {
existingRowsInDb.push(result);
});
});
book.updateMany(existingRowsInDb, (err,docs) => {
err ? console.log(err) : console.log(`updated ${docs.length}`);
});
}

Answer 1

Using promise you can do something like this:
function UpdateBulk(completeValidBooks) {
GetExistingRows(completeValidBooks).then((existingRowsInDb) => {
book.updateMany(existingRowsInDb, (err, docs) => {
err ? console.log(err) : console.log(`updated ${docs.length}`);
});
})
}
function GetExistingRows(completeValidBooks) {
return new Promise((resolve, reject) => {
var existingRowsInDb = [];
completeValidBooks.forEach((currentBook) => {
book.findOne({
'ISIN': currentBook.ISIN
}, (error, result) => {
existingRowsInDb.push(result);
});
});
resolve(existingRowsInDb);
})
}
Using callback you can do like this:
function UpdateBulk(completeValidBooks) {
GetExistingRows(completeValidBooks, (existingRowsInDb) => {
book.updateMany(existingRowsInDb, (err, docs) => {
err ? console.log(err) : console.log(`updated ${docs.length}`);
});
})
}
function GetExistingRows(completeValidBooks, callback) {
var existingRowsInDb = [];
completeValidBooks.forEach((currentBook) => {
book.findOne({
'ISIN': currentBook.ISIN
}, (error, result) => {
existingRowsInDb.push(result);
});
});
callback(existingRowsInDb);
}