JSON.parse fails on ObjectId - node.js

Question

I am trying to convert a string for use in mongodb but fails.
let pipeline = JSON.parse('[{"$match": {"_id": ObjectId("5b5637acbd3e9c2068ef80c3")}]');
// results in "SyntaxError: Unexpected token O in JSON at position 20"s
let pipeline = JSON.parse('[{"$match": {"_id": "5b5637acbd3e9c2068ef80c3"}]');
let response = await db.collect('<collection_name>').aggregate(pipeline).toArray();
// returns [] parse works but mongodb doesn't return any rows!
// This works but its not the solution I am looking for.
let pipeline = [{"$match": {"_id": ObjectId("5b5637acbd3e9c2068ef80c3")}];
let response = await db.collect('<collection_name>').aggregate(pipeline).toArray();
I tried using the BSON type but had no luck.
My current work around is to remove the ObjectId() from the string and use a Reviver function with JSON.parse
const ObjectId = require('mongodb').ObjectID;
let convertObjectId = function (key,value){
if (typeof value === 'string' && value.match(/^[0-9a-fA-F]{24}$/)){
return ObjectId(value);
} else {
return value;
};
}
let pipeline = JSON.parse('[{"$match": {"_id": "5b5637acbd3e9c2068ef80c3"}]',convertObjectId);
let response = await db.collect('<collection_name>').aggregate(pipeline).toArray();
// returns one record.

Answer 1

Unfortunately, [{"$match": {"_id": ObjectId("5b5637acbd3e9c2068ef80c3")}] is not valid JSON.
The value of a property in JSON can only be an object (ex.: {}), an array (ex.: []), a string (ex.: "abc"), a number (ex.: 1), a boolean (ex.: true), or null. See an example of these values here: https://en.wikipedia.org/wiki/JSON#Example.
What you could do is add ObjectId() manually after parsing the JSON. This would mean that the value of _id would be a string first, which is valid JSON.
Then, you can loop through your parsed JSON to add ObjectId (see reference here: https://mongodb.github.io/node-mongodb-native/api-bson-generated/objectid.html):
const ObjectId = require('mongodb').ObjectID;
const pipeline = JSON.parse('[{"$match": {"_id": "5b5637acbd3e9c2068ef80c3"}]');
const pipelineWithObjectId = pipeline.map(query => ({
$match: {
...query.$match,
_id: ObjectId(query.$match._id)
}
});
const response = await db.collect('<collection_name>').aggregate(pipelineWithObjectId).toArray();
This should work with the example you provided but there are multiple caveats:
Parsing a query like that could be a vulnerability if the string contains user input that has not been sanitized: https://blog.websecurify.com/2014/08/hacking-nodejs-and-mongodb.html.
This particular code snippet would only work for queries with $match, which means that this code is not very scalable.
This code is not elegant.
All these reasons, for what they are worth, make me think that you would be better off using an object rather than a string for your queries.