async await

mongodb.js

/**
 * Reset a collection by removing existing content and insert a default
 * set of documents.
 *
 * @param {string} dns     DNS to connect to database.
 * @param {string} colName Name of collection.
 * @param {string} doc     Documents to be inserted into collection.
 *
 * @throws Error when database hadnling fails.
 *
 * @return {Promise} Empty.
 */
async function resetCollection(dns, colName, doc) {
    const db  = await mongo.connect(dns);
    const col = await db.collection(colName);
    const op1 = await col.deleteMany();
    const op2 = await col.insertMany(doc);

    db.close();
}