Change binary subtype in MongoDB

Question

Is it possible to change only the subtype of the Binary element in MongoDB?
I have Binary element in database of type 0x00
BinData(0, xxx)
Is it possible via shell to update only the subType part of this element/change it to another value?

Or the only way is to create new property with old binary part?

new BinData(newVal, xxx)

Answer 1

No the only way is to create new BinData using the previous base64 value. Of course to get that value you only need to call the .base64() method.

> var bin = new BinData(3,"ASNFZ4mrze/+3LqYdlQyEA==")
> var newType = 0;
> bin = new BinData(newType, bin.base64());
BinData(0,"ASNFZ4mrze/+3LqYdlQyEA==")

The reason is that the type property is not writable as shown by the output of Object.getOwnPropertyDescriptor()

> Object.getOwnPropertyDescriptor(bin, 'type')
{
        "configurable" : true,
        "enumerable" : false,
        "value" : 0,
        "writable" : false
}

For example:

> bin.type;
0
> bin.type = 3;
3
> bin.type;
0

You can see that value of bin.type remains unchanged even after setting it to 3