在nodejs循环中每次更新后如何获取文档的新值？

Question

I'm trying to update collection many times in a loop but each time I get the value of oldRight not changed it gives the first value always.

I'm storing topics in mongodb using nested sets pattern.

 for(let name of level1) { console.log(name); var parent = 'root'; getParentAndAddTopic(name, parent, function (err, topic) { if (err) { console.log(err); } var oldRight = topic.right; console.log(oldRight); db.topics.create({name: name, parent: 'root', left: oldRight, right: oldRight + 1}, function (err, res) { if (err) throw err; }); db.topics.updateMany({right: {$gte: oldRight}}, {$inc: {right: 2}}, function (err, res) { if (err) throw err; }); }); function getParentAndAddTopic(name, parent, callback) { db.topics.find({name: 'root'}, function (err, topics) { if (err) { callback(err, null); } else { callback(null, topics[0]); } }); } }

Answer 1

Working with the database is an asynchronous function, you can't do it in a normal loop. And change var to let , using var is a bad practice leading to many problems.