Can I determine if a string is a MongoDB ObjectID?

Question

I am doing MongoDB lookups by converting a string to BSON. Is there a way for me to determine if the string I have is a valid ObjectID for Mongo before doing the conversion?

Answer 1

I found that the mongoose ObjectId validator works to validate valid objectIds but I found a few cases where invalid ids were considered valid. (eg: any 12 characters long string)

var ObjectId = require('mongoose').Types.ObjectId;
ObjectId.isValid('microsoft123'); //true
ObjectId.isValid('timtomtamted'); //true
ObjectId.isValid('551137c2f9e1fac808a5f572'); //true

What has been working for me is casting a string to an objectId and then checking that the original string matches the string value of the objectId.

new ObjectId('timtamtomted'); //616273656e6365576f726b73
new ObjectId('537eed02ed345b2e039652d2') //537eed02ed345b2e039652d2

This work because valid ids do not change when casted to an ObjectId but a string that gets a false valid will change when casted to an objectId.

Answer 2

@ross-u answer is just amazing.

I have chained the methods to do a full validation inline:

documentId = id && isValid(id) && new ObjectId(id) == id ? id : null

Note the double equal sign, which is VERY important as new ObjectId() does not return a string and strict comparison will return false when compared against a normal string (which I had coming in my logic).

The methods have been destructured from the mongoose object exposed by the require:

const {
  Types: {
    ObjectId: { isValid },
    ObjectId
  }
} = require("mongoose");

Answer 3

If you have the hex string you can use this:

ObjectId.isValid(ObjectId.createFromHexString(hexId));

Answer 4

Here is some code I have written based on @andy-macleod's answer.

It can take either an int or string or ObjectId and returns a valid ObjectId if the passed value is valid or null if it is invalid:

var ObjectId= require('mongoose').Types.ObjectId;

function toObjectId(id) {

    var stringId = id.toString().toLowerCase();

    if (!ObjectId.isValid(stringId)) {
        return null;
    }

    var result = new ObjectId(stringId);
    if (result.toString() != stringId) {
        return null;
    }

    return result;
}