Can I determine if a string is a MongoDB ObjectID?


Can I determine if a string is a MongoDB ObjectID?

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?

Here is the coffeescript for my current findByID function. It works great, but I’d like to lookup by a different attribute if I determine the string is not an ID.

db.collection "pages", (err, collection) ->
    _id: new BSON.ObjectID(id)
  , (err, item) ->
    if item
      res.send item
      res.send 404

Problem courtesy of: Will


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.

Solution courtesy of: Andy Macleod


Warning: isValid
will return true
for arbitrary 12/24 length strings beginning with a valid hex digit.
Currently I think this is a better check:

((thing.length === 24 || thing.length === 12) && isNaN(parseInt(thing,16)) !== true)

Discussion courtesy of: iss42

It took me a while to get a valid solution as the one proposed by @Andy Macleod of comparing objectId value with its own string was crashing the Express.js server on:

var view_task_id_temp=new mongodb.ObjectID("invalid_id_string"); //this crashed

I just used a simple try catch to solve this.

var mongodb = require('mongodb');
var id_error=false;
    var x=new mongodb.ObjectID("57d9a8b310b45a383a74df93");

   // Do stuff here

Discussion courtesy of: Vibhu

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;

Discussion courtesy of: nzjoel

If you have the hex string you can use this:


Discussion courtesy of: pkarc

You can use a regular expression to test for that:


if id.match /^[0-9a-fA-F]{24}$/
    # it's an ObjectID
    # nope


if (id.match(/^[0-9a-fA-F]{24}$/)) {
    // it's an ObjectID    
} else {
    // nope    

Discussion courtesy of: JohnnyHK

I have used the native node mongodb driver to do this in the past. The isValid method checks that the value is a valid BSON ObjectId. See the documentation here.

var ObjectID = require('mongodb').ObjectID;
console.log( ObjectID.isValid(12345) );

Discussion courtesy of: cbaigorri

This recipe can be found in it’s original form on Stack Over Flow



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Can I determine if a string is a MongoDB ObjectID?