JSFiddle - React, Tailwind, and code Playground

HTML

<button class="mybtnClass" value="red">red</button> 
<button class="mybtnClass" value="green">green</button>

JavaScript

var buttons = document.getElementsByClassName('mybtnClass');

for (var i=buttons.length; i--;) {
    buttons[i].addEventListener('click', myFunction, false);
}

function myFunction() {
 alert(this.value);   
}