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

In the solution answer Andy Macleod said:

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.

An implementation of this approach, would be a function that checks if the passed value is a valid ObjectId and works with both string and ObjectId (object) values. It would look something like this:

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

function isValidObjectId(value) {
  // If value is an object (ObjectId) cast it to a string
  var valueString = typeof value === "string" ? value : String(value); 

  // Cast the string to ObjectId
  var idInstance = new ObjectId(valueString); 

  return String(idInstance) === valueString;
}