MongoJS Insert Method Not Creating Collection in MongoDB & Robo 3T

I am using MongoJS and would like to auto-create a new collection called "Comments" in my MongoDB via the code below...Not working and can't seem to figure out why. Thanks for any insight you can provide!

      app.post("/post", function(req, res) {
        db.comments.insert({
          articleId: JSON.stringify(req.body._Id),
          name: JSON.stringify(req.body.chatId),
          message: JSON.stringify(req.body.message)
        }),function(err, response) {
          if(err) {
            console.log(err); 
          } else {
            console.log("This is working!");
          }
        }}); 

If you use the body-parse middleware:

app.post("/post", function(req, res) {
    let { body } = req;
    db.comments.insert({
      articleId: body._Id,
      name: body.chatId,
      message: body.message
    }),function(err, response) {
      if(err) {
        console.log(err); 
      } else {
        console.log("This is working!");
      }
    }});

and if not , just use it like:

let parsed;
try {
  parsed = JSON.parse(res.text)
} catch(err){req.send(err)}
// now you have:
parsed._Id ...