how to edit clicked button style code example

Example 1: css onclick change color

<style>
.dabutton:focus {
    background-color:yellow;
}
</style>
<button class="dabutton"></button> // <-- usage

Example 2: how to change the text in a button on onclick

var btn = document.getElementById("mybtn");
btn.value = 'my value'; // will just add a hidden value
btn.innerHTML = 'my text';