how to add an event with javascrtipt to a class code example

Example 1: event listener to elements with class

document.querySelectorAll('.some-class').forEach(item => {
  item.addEventListener('click', event => {
    //handle click
  })
})

Example 2: javascript add listeners to class

var classname = document.getElementsByClassName("classname");

var myFunction = function() {
    var attribute = this.getAttribute("data-myattribute");
    alert(attribute);
};

for (var i = 0; i < classname.length; i++) {
    classname[i].addEventListener('click', myFunction, false);
}