Detect click inside/outside of element with single event handler

Here's a one liner that doesn't require jquery using Node.contains:

// Get arbitrary element with id "my-element"
var myElementToCheckIfClicksAreInsideOf = document.querySelector('#my-element');
// Listen for click events on body
document.body.addEventListener('click', function (event) {
    if (myElementToCheckIfClicksAreInsideOf.contains(event.target)) {
        console.log('clicked inside');
    } else {
        console.log('clicked outside');
    }
});

If you're wondering about the edge case of checking if the click is on the element itself, Node.contains returns true for the element itself (e.g. element.contains(element) === true) so this snippet should always work.

Browser support seems to cover pretty much everything according to that MDN page as well.

Using jQuery:

$(function() {
  $("body").click(function(e) {
    if (e.target.id == "myDiv" || $(e.target).parents("#myDiv").length) {
      alert("Inside div");
    } else {
      alert("Outside div");
    }
  });
})

#myDiv {
  background: #ff0000;
  width: 25vw;
  height: 25vh;
}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<div id="myDiv"></div>