Hovik,
<!DOCTYPE html>
<html>
<head>
<title>Untitled</title>
<meta charset="utf-8">
<style type="text/css">
</style>
<script>
document.addEventListener("DOMContentLoaded", function() {
document.querySelector(".pages").addEventListener("click", function(event) {
var target = event.target;
if (target = target.closest(".page")) {
var index = [].indexOf.call(document.querySelectorAll(".pages .page"), target), str = 20 - index * 2 + "%";
document.querySelector(".action span").innerHTML = str;
if (target.querySelector("img")) {
alert("heloo world");
}
}
});
});
</script>
</head>
<body>
<div class="pages">
<div class="page"><img src="#" alt="#">кнопка 1</div>
<div class="page"><span class="page-txt">кнопка 2</span></div>
<div class="page"><span class="page-txt">кнопка 3</span></div>
<div class="page"><span class="page-txt">кнопка 4</span></div>
<div class="page"><span class="page-txt">кнопка 5</span></div>
<div class="page"><span class="page-txt">кнопка 6</span></div>
<div class="page"><span class="page-txt">кнопка 7</span></div>
<div class="page"><span class="page-txt">кнопка 8</span></div>
<div class="page"><span class="page-txt">кнопка 9</span></div>
<div class="page"><span class="page-txt">кнопка 10</span></div>
</div>
<div class="action">
<span></span>
</div>
</body>
</html>