Ignore _id in mongoose subdocuments

[mauliksoneji]

I find this library really helpful in storing history of documents.

However, when there are any changes made to the document and we pass in a Javascript object, mongoose will replace the old _id properties in subdocument and replace it with new values.

For example:
I have a document as follows:

"completionCriteria": [
    {
        "formula" : {
            "quantifier" : "all"
        },
        "_id" : ObjectId("5996d4524d98c8001558c7b9"),
        "action" : "complete",
        "requiredCondition" : "complete"
    },
    {
        "formula" : {
            "quantifier" : "any"
        },
        "_id" : ObjectId("5996d4524d98c8001558c7b8"),
        "action" : "inComplete",
        "requiredCondition" : "inComplete"
    },
    {
        "formula" : {
            "quantifier" : "all"
        },
        "_id" : ObjectId("5996d4524d98c8001558c7b7"),
        "action" : "notAttempted",
        "requiredCondition" : "notAttempted"
    }
]

Now when I change the document without making any changes to the completionCriteria array, the array remains the same but the _id property array elements change and thus this gets mentioned in History document as follows:

"completionCriteria": {
    "0" : {
        "_id" : [ 
            "5996d4524d98c8001558c7b9", 
            "5996d4914d98c8001558c7d5"
        ]
    },
    "1" : {
        "_id" : [ 
            "5996d4524d98c8001558c7b8", 
            "5996d4914d98c8001558c7d4"
        ]
    },
    "2" : {
        "_id" : [ 
            "5996d4524d98c8001558c7b7", 
            "5996d4914d98c8001558c7d3"
        ]
    },
    "_t" : "a"
}

Is there any way to ignore the _id property because this is automatically generated by mongoose and thus can be ignored?

[mimani]

Ideally _id should not had changed as there are no changes in the completionCriteria array. I see a similar question here, not sure it will help. In case if you don't need _id for every element in the array, If not you can disable it as explained here.

I have not added such feature to ignore some fields, but it can be done easily by adding propertyfilter in the diff function I am using here.

[mauliksoneji]

Thanks for the early reply.

I haven't tried using the propertyFilter that you discussed above, but I wrote a function that would ignore _id property in JSON.stringify step as follows:

function replacer(key, value) {
  // Filtering out properties
  if (key === '_id') {
    return undefined;
  }
  return value;
}
const diff = jsondiffpatch.diff(JSON.parse(JSON.stringify(original, replacer)),
    JSON.parse(JSON.stringify(updated, replacer)));

Thanks again for the help, I am closing the issue.