Key.js

const projectId = <YourProjectID>;
const locationId = <YourPreferedStorageLocationID>; //Based on the google cloud regions e.g. us-central1
const keyRingId = <KeyRingID>;

const kmsClient = new KeyManagementServiceClient();

const locationName = kmsClient.locationPath(projectId, locationId);

async function createKeySymmetricEncryptDecrypt() {
    const keyRingName = await kmsClient.keyRingPath(projectId, locationId, keyRingId);
    const [key] = await kmsClient.createCryptoKey({
        parent: keyRingName,
        cryptoKeyId: <YourKeyId>,
        cryptoKey: {
            purpose: 'ENCRYPT_DECRYPT',
            versionTemplate: {
                algorithm: 'GOOGLE_SYMMETRIC_ENCRYPTION',
            },
        },
    });

    console.log(`Created symmetric key: ${key.name}`);
}