Develop a Node.js application that connects to a Cassandra database, creates a table called "employees", and inserts sample employee records into the table. The employees should have fields such as id, name, age, and department.

To create a Node.js application that connects to a Cassandra database, you'll need to follow these steps:

1. Install the required packages
2. Set up the connection to the Cassandra cluster
3. Create a keyspace (if not already created)
4. Create the "employees" table
5. Insert sample employee records into the table

Here's an example of how you can achieve this:

1. First, install the `cassandra-driver` package using npm:

```bash
npm init -y
npm install cassandra-driver
```

2. Next, create a new file called `app.js` and set up the connection to your Cassandra cluster:

```javascript
const cassandra = require('cassandra-driver');

const client = new cassandra.Client({
  contactPoints: ['127.0.0.1'], // Replace with your Cassandra cluster IPs
  localDataCenter: 'datacenter1', // Replace with your data center name
  keyspace: 'mykeyspace' // Replace with your desired keyspace name
});

client.connect((err) => {
  if (err) {
    console.error('Error connecting to Cassandra:', err);
    return;
  }
  console.log('Connected to Cassandra');
});
```

3. Now, let's create the keyspace (if it doesn't exist):

```javascript
const createKeyspaceQuery = `
  CREATE KEYSPACE IF NOT EXISTS mykeyspace
  WITH replication = {'class': 'SimpleStrategy', 'replication_factor': '1'}
`;

client.execute(createKeyspaceQuery, (err) => {
  if (err) {
    console.error('Error creating keyspace:', err);
    return;
  }
  console.log('Keyspace created');
});
```

4. After that, create the "employees" table:

```javascript
const createTableQuery = `
  CREATE TABLE IF NOT EXISTS mykeyspace.employees (
    id UUID PRIMARY KEY,
    name TEXT,
    age INT,
    department TEXT
  )
`;

client.execute(createTableQuery, (err) => {
  if (err) {
    console.error('Error creating table:', err);
    return;
  }
  console.log('Employees table created');
});
```

5. Finally, insert sample employee records into the "employees" table:

```javascript
const employees = [
  { id: cassandra.types.uuid(), name: 'John Doe', age: 30, department: 'HR' },
  { id: cassandra.types.uuid(), name: 'Jane Smith', age: 28, department: 'IT' },
];

const insertEmployeeQuery =
  'INSERT INTO mykeyspace.employees (id, name, age, department) VALUES (?, ?, ?, ?)';

employees.forEach((employee) => {
  client.execute(
    insertEmployeeQuery,
    [employee.id, employee.name, employee.age, employee.department],
    { prepare: true },
    (err) => {
      if (err) {
        console.error('Error inserting employee:', err);
        return;
      }
      console.log(`Inserted employee ${employee.name}`);
    }
  );
});

// Close the connection after a few seconds to allow all queries to complete
setTimeout(() => {
  client.shutdown();
}, 5000);
```

Now you can run your Node.js application with `node app.js`. This will connect to your Cassandra cluster, create the keyspace and "employees" table (if they don't exist), and insert the sample employee records.

Remember to replace the contact points, data center name, and keyspace name with your own values.