DOM - ALERT

<!DOCTYPE html>
<html>
<style>
body{
    display:flex;
    align-items: center;
    justify-content: center;
}
</style>
<body>

<input type="text" id="name">

<button onclick="greet()">Greet</button>

<h4 id="message"></h4>

<script>
function greet() {

    const input = document.getElementById("name");
    const name = input.value;
    const message = document.getElementById("message");

    if (name == "") {
       message.innerText="Please enter text!"
    }
    else {
         message.innerHTML = '<img src="https://pbs.twimg.com/media/FgOkmTFaYAAGzYY.jpg" width="250">';
    }

}
</script>

</body>
</html>