A JavaScript to illustrate insert/find operations while using MongoDB client-side field level encryption with automatic encryption feature.

csfle-automatic-encryption.js

// NOTE: In the explicit encryption method all insert/update/find operations should ship encrypted data.
// Let's explore an MongoDB Enterprise that helps automatically encryption / decryption data for you. But first,
// define a JSON schema mapping for our patients collection via the Field-Level option.
const healthCareAppSchema = {
  "health_care_app.patients": {
    "bsonType": "object",
    "properties": {
      "medRecNum": {
        "bsonType": "int"
      },
      "firstName": {
        "bsonType": "string"
      },
      "lastName": {
        "bsonType": "string"
      },
      "ssn": {
        "encrypt": {
          "bsonType": "string",
          "algorithm": SSN_ENCRYPTION_ALGORITHM,
          "keyId": [SSN_ENCRYPTION_KEY_UUID]
        }
      },
      "mobile": {
        "encrypt": {
          "bsonType": "string",
          "algorithm": MOBILE_ENCRYPTION_ALGORITHM,
          "keyId": [MOBILE_ENCRYPTION_KEY_UUID]
        }
      },
      "comment": {
        "bsonType": "string"
      }
    }
  }
};
// lets recreate the client-side Field-Level encryption options with schemaMap
var csfleOptionsWithSchema = {
  "keyVaultNamespace" : "encryption.__dataKeys",
  "kmsProviders" : {
    "local" : {
      "key" : BinData(0, LOCAL_KEY)
    }
  },
  "schemaMap" : healthCareAppSchema
};
var csfleClient = Mongo("mongodb://localhost:28000", csfleOptionsWithSchema);
var csfleDB = csfleClient.getDB("health_care_app");

// insert a new record patient record
// Notice that values being inserted are in plain text.
csfleDB.getCollection("patients").insert({
  "_id": 7,
  "medRecNum": 7,
  "firstName": "James",
  "lastName": "Bond",
  "ssn": "777-77-7777",
  "mobile": "777-777-7777",
  "comment": "James Bond SSN/Phone are automatically encrypted."
});

// note the plainDB client shows that data is stored in BinData
var plainDB = plainClient.getDB("health_care_app");
plainDB.getCollection("patients").findOne({"_id": 7});
/*
{
  "_id" : 7,
  "medRecNum" : 7,
  "firstName" : "James",
  "lastName" : "Bond",
  "ssn" : BinData(6,"AWE7iEZXVUV9my4XXm0O38sCR6xSEF8KA8kLZEMlCdCszXK/tqSWKOm30I34OHp5Bssc2CZy4eOhyPRRFfRziu+HvRHtqs9FDxSJ/9ER9zLLwJ/Izy5UoHHbJFIk99tRY3s="),
  "mobile" : BinData(6,"AjtqXpdbrUKmnslCbIXOtZUC81TuNTJSB3Gq3c6GFETMreRZJPCZOuzUdfI0gLpovBf1ISgGBQrfNWGUBP78qCnpMfkc1Wijnwio8sQK8stk0yNQawlmp8NA9yGHsphXuDQ="),
  "comment" : "James Bond SSN/Phone are automatically encrypted."
}
*/

// Find patient by plain SSN returns the data.
// Note: The find operation is also using the plain text. But the field values
// in the filter are automatically encrypted before sending the query to server
csfleDB.getCollection("patients").findOne({"ssn": "111-11-1111"})
/*
{
  "_id" : 1,
  "medRecNum" : 1,
  "firstName" : "John",
  "lastName" : "Doe",
  "ssn" : "111-11-1111",
  "mobile" : "111-111-1111",
  "comment" : "John Doe's SSN/Phone are manually encrypted."
}
*/