Getting null ObjectID from MongoDB using findByID in javascript - newbie

Question

I am new to javascript and mongo and trying to find a course in my MongoDB database collection using id but getting null. Could you please help me with this?

Note: I am using MacBook. This is a very basic thing I am trying to do. I am able to fetch the object using .find() but findByID(id) doesn't seem to work for me. What am I missing? Let me know if any more detail is required.

Edit: A weird observation, refer the image. For the first one, I cannot find it or update it using id but I could find and update the second one. The first one was inserted in database using json file and second one was inserted using .save() in javascript.

PFB my code:

const mongoose = require('mongoose');

mongoose.connect('mongodb://localhost/mongo-exercise', { useNewUrlParser: true, useUnifiedTopology: true })
    .then(() => console.log('Connected to mongo-exercise database.'))
    .catch(err => console.log('Could not connect to mongo-exercise database.', err));

// Create the schema
const schema = new mongoose.Schema({
    name: String,
    author: String,
    price: Number,
    tags: [String],
    isPublished: Boolean
});

// Call the schema
const Course = mongoose.model('course', schema);

async function updateCourse(id) {
    try {
        const course = await Course
            .findById(id);
        console.log('Course is ', course);
    }
    catch (err) {
        console.log('Solution failed: ', err.message);
        throw error
    }
}

updateCourse("5a68fdf95db93f6477053ddd");

[ enter image description here ]

MongoDB _id fields are usually type ObjectId, not string. Try updateCourse(ObjectId("5a68fdf95db93f6477053ddd")); — Joe
– Joe, Commented May 18, 2020 at 23:52
@Joe : . findById() takes in a string & internally it does convert string to ObjectId() prior to querying DB.. — whoami - fakeFaceTrueSoul
– whoami - fakeFaceTrueSoul, Commented May 18, 2020 at 23:58
That is good to know! So I've been wasting the effort to convert all this time. — Joe
– Joe, Commented May 19, 2020 at 0:01
@Joe : Yes, it's a wrapper func provided by mongoose, useful when you're querying only with _id.. — whoami - fakeFaceTrueSoul
– whoami - fakeFaceTrueSoul, Commented May 19, 2020 at 0:03
@Vers : If your _id field in database is of type ObjectId() then use .findById() else if your _id field is type string in database then use .findOne({_id : someInputString}) but you need to remember that type of input should match with type of _id field in DB. Also do not maintain _id in two different types in DB either maintain it as string or ObjectId() for all the docs, I would say to maintain it as ObjectId() - let MongoDB create it for docs when they got inserted.. — whoami - fakeFaceTrueSoul
– whoami - fakeFaceTrueSoul, Commented May 19, 2020 at 4:59

Jjhok Anderson · Accepted Answer · 2020-05-19 01:11:49Z

1

Happened to me.when importing using compass, just deselect the _Id property as its a string. When imported mongodb driver will put in a new object _id with and objectid that can be queried.

answered May 19, 2020 at 1:11

Jjhok Anderson

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1 Comment

Vers Over a year ago

Thank you for pointing that out. What you suggested was correct but it still doesn't let me find by id :(

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