You can use JavaScript and Node.js to send WhatsApp messages programmatically using Twilio's Messaging API. To start, you need to sign up for a Twilio account, activate the WhatsApp Sandbox, and install the required software, including Node.js, npm, and the Twilio Node library. You also need to set environment variables with your Twilio account credentials. With these steps complete, you can create a file called index.js that uses the Twilio library to send a WhatsApp message from your personal phone number to a predefined phone number in the Sandbox. After running the code, you should see the sent message in your messages. Note that there are other languages and blog posts available for sending WhatsApp messages using different programming languages.