Regex for MongoDB ObjectID

Question

With reference to this SO question, I have a scenario where I only need to match a hex string with a-f included. All else should not match. Example:

checkForHexRegExp.test("112345679065574883030833"); // => false
checkForHexRegExp.test("FFFFFFFFFFFFFFFFFFFFFFFF"); // => false
checkForHexRegExp.test("45cbc4a0e4123f6920000002"); // => true

My use case is that I am working with a set of hex strings and would like to only validate as true those that are mongodb objectIDs.

`112345679065574883030833`, `FFFFFFFFFFFFFFFFFFFFFFFF` are also valid hexadecimal representations. Why `false` for those strings? — falsetru, Jan 08 '14 at 06:36
@falsetru As per my use case, I need a regex that will only match mongodb ObjectIDs. — gmajivu, Jan 08 '14 at 06:38
As answerd by @olegshparber all the above IDs form a valid mongodb object ID please refer to mongodb Object ID documentation — pshirishreddy, Jan 08 '14 at 06:58
@gabeno I still don't understand what you're trying to do as all three are valid MongoDB ObjectIDs. — JohnnyHK, Jan 08 '14 at 13:39
He wants to match MongoDB ObjectIDs in practice, not in theory. — tadasajon, Jun 02 '15 at 02:27

score 108 · Accepted Answer · edited Aug 18 '17 at 20:02

108

You can use following regular expression but it will not quite work

checkForHexRegExp = /^(?=[a-f\d]{24}$)(\d+[a-f]|[a-f]+\d)/i

Example:

> checkForHexRegExp.test("112345679065574883030833")
false
> checkForHexRegExp.test("FFFFFFFFFFFFFFFFFFFFFFFF")
false
> checkForHexRegExp.test("45cbc4a0e4123f6920000002")
true

But, as I commented, 112345679065574883030833, FFFFFFFFFFFFFFFFFFFFFFFF are also valid hexadecimal representations.

You should use /^[a-f\d]{24}$/i because it passes all the above tests

edited Aug 18 '17 at 20:02

John Culviner

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answered Jan 08 '14 at 06:50

falsetru

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is `i` flag required? – Sang Feb 02 '18 at 19:15
1

@transang, Yes it is. (to ignore case) – falsetru Feb 02 '18 at 23:15
1

It could be removed though, but that'd make the regex itself longer `/^[a-fA-F\d]{24}$/`. Not sure what the performance impact is, but I assume if there is one, it'll be minimal (at least in this case) – Stephan Bijzitter Apr 13 '21 at 12:14
ObjectId.TryParse returns true for "FFFFFFFFFFFFFFFFFFFFFFFF" – Kishan Vaishnav May 27 '21 at 07:19
@KishanVaishnav, I don't know what `TryParse` is. I think it's not a javascript method. (This question is tagged javascript). How about post a separate question? – falsetru May 27 '21 at 08:52
1

Sorry, it is a C# method. I just wanted to assert that the Mongo Driver seem to think that it is a valid ObjectId. – Kishan Vaishnav May 27 '21 at 08:55

Vasili Syrakis · Answer 2 · 2014-01-08T06:41:00.913

22

I need a regex that will only match mongodb ObjectIDs

If you need that, you will have to specify exactly what makes up a mongodb ObjectID, so that we can create the appropriate regex string for it.

This should technically work in js:

var myregexp = /^[0-9a-fA-F]{24}$/;
subject = "112345679065574883030833";

if (subject.match(myregexp)) {
    // Successful match
} else {
    // Match attempt failed
}

edited Jan 08 '14 at 06:41

answered Jan 08 '14 at 06:33

Vasili Syrakis

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Oleg Shparber · Answer 3 · 2014-01-08T07:04:25.973

Technically, all examples in the question potentially could be valid ObjectIds. If you have to add some additional verification and that regexp is not enough, then my suggestion is to check if the first 4 bytes are a valid timestamp. You can even verify that ObjectId has been generated during a certain period of time (e.g. since your project has been started or so). See ObjectId documentation for details.

If there's another timestamp field in an object, then it's also possible to make sure that both times are really close.

Just for the reference, in MongoDB shell ObjectId::getTimestamp() method can be used to extract a timestamp from ObjectId.

Amarnath Krishnan · Answer 4 · 2014-01-08T07:18:55.250

3

I would do something like this

function validateObjectId(id)
{
    var bool=false; 
    if(id.length==24) bool=/[a-f]+/.test(id);
    return bool;
}


> validateObjectId("112345679065574883030833")
  false
> validateObjectId("FFFFFFFFFFFFFFFFFFFFFFFF")
  false
> validateObjectId("45cbc4a0e4123f6920000002")
  true
> validateObjectId("45cbc4a0e4123f6920")
  false

edited Jan 08 '14 at 07:18

answered Jan 08 '14 at 07:07

Amarnath Krishnan

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`validateObjectId("ffffffffffffffffffffffff")` returns `true` – Kevin Beal Apr 22 '21 at 17:49

score 0 · Answer 5 · answered May 20 '23 at 10:01

0

For those who was looking just for hex checking the string:

s := "5fa0ef460c2056137465a39b"
if _, err := hex.DecodeString(s); err == nil {
    fmt.Println("ok")
}

answered May 20 '23 at 10:01

Dmitriy Botov

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Regex for MongoDB ObjectID

5 Answers5

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