event listener to elements with 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);
}

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

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

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

// If you have ES6 support you can replace your last line with:

    Array.from(elements).forEach(function(element) {
      element.addEventListener('click', myFunction);
    });

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