display a message based on the time of the day in javascript?

You can display a message based on the time of the day in JavaScript using the `Date` object to get the current hour. Here's how you can do it:

```javascript
function getMessageByTime() {
    const hour = new Date().getHours();

    if (hour >= 5 && hour < 12) {
        return "Good morning!";
    } else if (hour >= 12 && hour < 18) {
        return "Good afternoon!";
    } else {
        return "Good evening!";
    }
}

// Example usage
const message = getMessageByTime();
console.log(message); // Output depends on the current time of the day
```

In this code:
- We create a function `getMessageByTime` that determines the current hour using `new Date().getHours()`.
- Based on the hour, we return different messages for morning, afternoon, and evening.
- We then call the function and store the message in a variable, and finally log the message to the console.