JSFiddle - React, Tailwind, and code Playground

HTML

<input type="button" class="mainButton" id="button_id" />

JavaScript

function addEvents()
{
    var buttonArray = document.getElementsByClassName('mainButton');
    for(i = 0; i < buttonArray.length; i++)
    {
        if (document.addEventListener) {
            buttonArray[i].addEventListener("click", myFunction);
        } 
        else { 
            if (document.attachEvent) {
                buttonArray[i].attachEvent("onclick", myFunction);
            }
        }
    }
}

function myFunction(e) {
    alert("Button " + e.target.id + " was clicked.");
}

addEvents();