Янковиц,
<!DOCTYPE HTML>
<html>
<head>
<title>Untitled</title>
<meta charset="utf-8">
<style>
body {
display: flex;
margin: 0;
height: 100vh;
background: #56bddc;
}
.box {
display: flex;
margin: auto;
box-shadow: 0 0 5px hsla(0, 0%, 0%, .25);
}
.el {
width: 60px;
line-height: 60px;
font-family: consolas;
font-size: 30px;
text-align: center;
cursor: pointer;
background: #fff;
-webkit-user-select: none;
user-select: none;
-moz-user-select: none;
}
.el:hover { background: #fece9a; }
.mark { background: #fece9a; }
.blue, .blue:hover{
background: #0000FF;
}
</style>
<script>
window.addEventListener("DOMContentLoaded", function() {
[].forEach.call(document.querySelectorAll(".box"), function(item) {
var temp;
item.addEventListener("click", function(event) {
var el = item.querySelectorAll(".el");
target = event.target;
var index = [].indexOf.call(el, target);
if (index !== -1) {
[].forEach.call(el, function(el) {
el.classList.remove("blue");
});
if (temp == index) {
temp = void 0;
} else {
if (void 0 === temp) {
target.classList.add("blue");
temp = index;
} else {
var min = Math.min(index, temp), max = Math.max(index, temp);
el = [].slice.call(el, min, ++max);
[].forEach.call(el, function(el) {
el.classList.add("blue");
});
temp = void 0;
}
}
}
});
item.addEventListener("mouseover", function(event) {
var el = item.querySelectorAll(".el");
target = event.target;
var index = [].indexOf.call(el, target);
if (index !== -1) {
if (void 0 !== temp) {
[].forEach.call(el, function(el) {
el.classList.remove("blue");
});
var min = Math.min(index, temp), max = Math.max(index, temp);
el = [].slice.call(el, min, ++max);
[].forEach.call(el, function(el) {
el.classList.add("blue");
});
}
}
});
item.addEventListener("mouseleave", function(event) {
var el = item.querySelectorAll(".el");
if (temp) {
[].forEach.call(el, function(el) {
el.classList.remove("blue");
});
el[temp].classList.add("blue");
temp = void 0;
}
});
});
});
</script>
</head>
<body>
<div class='box'>
<div class='el'>1</div>
<div class='el'>2</div>
<div class='el'>3</div>
<div class='el'>4</div>
<div class='el'>5</div>
<div class='el'>6</div>
<div class='el'>7</div>
<div class='el'>8</div>
<div class='el'>9</div>
<div class='el'>X</div>
</div>
</body>
</html>