Layered Event Listeners

index.html

<fieldset>
    <legend>Layered Event Listeners</legend>
    <div class="box under" id="under"></div>
    <div class="box over" id="over"></div>
</fieldset>

Layered-Event-Listeners.markdown

Layered Event Listeners

Detect user events on obscured elements.

A Pen by Gerald on CodePen.

License.

script.js

var
    under = document.getElementById("under"),
    over  = document.getElementById("over")
;

under.addEventListener('mouseenter', function (e){
    $(this).addClass('circle');
});
under.addEventListener('mouseleave', function (e) {
    $(this).removeClass('circle');
});

over.addEventListener('mousemove', function (e) {
    this.style.visibility = "hidden";
    var elem = document.elementFromPoint(e.clientX, e.clientY);
    this.style.visibility = "visible";
    $(this).addClass('circle');
    if(elem.id === under.id) {
        under.dispatchEvent(new Event('mouseenter'));
    } else {
        under.dispatchEvent(new Event('mouseleave'));
    };
});
over.addEventListener('mouseleave', function (e) {
    $(this).removeClass('circle');
});

style.css

html {
  font-size: 62.5%;
}
body {
  font-size: 1.6rem;
  font-family: Helvetica, sans-serif;
}
legend {
  text-align: center;
  font-weight: bold;
  font-size: 3.5rem;
}
fieldset {
  position: relative;
  border: 1px solid #ccc;
  border-radius: 1rem;
  padding: 2rem;
}
.box {
  position: relative;
  margin: 0 auto;
  width: 100px;
  height: 100px;
  transition: border-radius .3s ease;
}
.circle {
  border-radius: 50px;
}
.under {
  top: 25px;
  left: -25px;
  background-color: rgba(255, 0, 0, 0.75);
  box-shadow: 0 1px 2px 0 rgba(0, 0, 0, 0.75);
}
.over {
  top: -25px;
  left: 25px;
  background-color: rgba(0, 0, 255, 0.75);
  box-shadow: 0 1px 8px 1px rgba(0, 0, 0, 0.75);
}