how can we remove data from keys mongodb code example

Example 1: remove property mongodb

db.myCollection.update({}, {$unset: {fieldToRemove:1}} , {multi: true});

Example 2: mongodb delete document where field exists

db.users.remove({
    "$or": [
        { "firstName": { "$exists": false } },
        { "lastName": { "$exists": false } }
    ]
})