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
– falsetru, Commented Jan 8, 2014 at 6:36
@falsetru As per my use case, I need a regex that will only match mongodb ObjectIDs. — gmajivu
– gmajivu, Commented Jan 8, 2014 at 6:38
As answerd by @olegshparber all the above IDs form a valid mongodb object ID please refer to mongodb Object ID documentation — pshirishreddy
– pshirishreddy, Commented Jan 8, 2014 at 6:58
@gabeno I still don't understand what you're trying to do as all three are valid MongoDB ObjectIDs. — JohnnyHK
– JohnnyHK, Commented Jan 8, 2014 at 13:39
He wants to match MongoDB ObjectIDs in practice, not in theory. — tadasajon
– tadasajon, Commented Jun 2, 2015 at 2:27

John Culviner · Accepted Answer · 2017-08-18 20:02:36Z

116

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, 2017 at 20:02

John Culviner

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answered Jan 8, 2014 at 6:50

falsetru

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6 Comments

Sang Over a year ago

is i flag required?

falsetru Over a year ago

@transang, Yes it is. (to ignore case)

Stephan Bijzitter Over a year ago

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)

Kishan Vaishnav Over a year ago

ObjectId.TryParse returns true for "FFFFFFFFFFFFFFFFFFFFFFFF"

Kishan Vaishnav Over a year ago

Sorry, it is a C# method. I just wanted to assert that the Mongo Driver seem to think that it is a valid ObjectId.

|

Vasili Syrakis · Accepted Answer · 2014-01-08 06:41:00Z

31

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 8, 2014 at 6:41

answered Jan 8, 2014 at 6:33

Vasili Syrakis

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Comments

Oleg Shparber · Accepted Answer · 2014-01-08 07:04:25Z

5

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.

edited Jan 8, 2014 at 7:04

answered Jan 8, 2014 at 6:43

Oleg Shparber

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Comments

Amarnath Krishnan · Accepted Answer · 2014-01-08 07:18:55Z

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 8, 2014 at 7:18

answered Jan 8, 2014 at 7:07

Amarnath Krishnan

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1 Comment

Kevin Beal Over a year ago

validateObjectId("ffffffffffffffffffffffff") returns true

Dmitriy Botov · Accepted Answer · 2023-05-20 10:01:36Z

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, 2023 at 10:01

Dmitriy Botov

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