To check your Twilio account balance using JavaScript, you'll need to set up a Node.js project and install the necessary dependencies, including the Twilio Node Helper Library and dotenv. You'll then create environment variables for your Twilio Account SID and Auth Token, retrieve your account balance using the Twilio client, and log the result to the console. Once you've completed these steps, you can run your script and view your account balance in real-time.