array of objects won't POST into mongodb - node.js

Question

I have an array of objects that is defined in mongoose schema as
blacklistGroup: {
userId: { type: String },
username: { type: String }
}
I can't figure out why it won't POST into mongodb.
I have a console.log that shows that it represents it's schema, but it never appears in mongodb? What am I doing wrong?
console.output
req.body.blacklistGroup
[ { userId: '5e2350c7f88cfb331c4f67de', username: 'artist1' },
{ userId: '5e20c5a139a92512cc7df63c', username: 'artist' } ]
[object Object]
app.js
app.post("/api/listings", checkAuth, (req, res, next) => {
console.log("req.body.blacklistGroup");
console.log(req.body.blacklistGroup);
let blacklistGroup = req.body.blacklistGroup;
console.log("req.body.blacklistGroup");
const post = new Post({
blacklistGroup: req.body.blacklistGroup,
});
//saves to database with mongoose
post.save().then(result => {
console.log(result);
res.status(201).json({
message: "Auction listing created successfully!",
postId: result._id
});
});
});

Answer 1

You can store all user at once. use mongoose insertMany
const Post = require('post'); //mongoose schema
app.post("/api/listings", checkAuth,(req, res, next) => {
console.log("req.body.blacklistGroup");
console.log(req.body.blacklistGroup);
let blacklistGroup = req.body.blacklistGroup;
console.log("req.body.blacklistGroup");
const blacklistGroup = req.body.blacklistGroup;
(async function(){
await Post.insertMany(blacklistGroup);
res.status(200).send('Ok');
})();
});
Or you can use
const Post = require('post'); //mongoose schema
app.post("/api/listings", checkAuth,async (req, res, next) => {
console.log("req.body.blacklistGroup");
console.log(req.body.blacklistGroup);
let blacklistGroup = req.body.blacklistGroup;
console.log("req.body.blacklistGroup");
const blacklistGroup = req.body.blacklistGroup;
await Post.insertMany(blacklistGroup);
res.status(200).send('Ok');
});
For More Here

Answer 2

You don't have an array of objects (or at least you don't want one), you have an object with two properties; userId and username. MongoDB is expecting JSON and it looks like you're trying to send it an array containing that object.
Try this:
let blacklistGroup = req.body.blacklistGroup[0];
To process an array of objects passed as req.body.blacklistGroup, you will have to iterate over it, define a new Post for each object and then send it. I think part of the confusion here is that your Schema is called blacklistGroup but it doesn't refer to a group, it refers to one entry.
const dbCalls = blacklistGroup.map(userObject => {
const post = new Post({
blacklistGroup: {
userId: userObject.userId,
username: userObject.username
});
return new Promise((resolve, reject) => {
post.save.then(() => {
resolve();
})
.catch(err => {
reject(err);
})
})
});
Promise.all(dbCalls).then(() => {
res.status(201).json({message: "Auction listings created successfully!"})
})
.catch(err => {
res.status(500).json({error: err})
});