MouseEvent: relatedTarget property

The MouseEvent.relatedTarget read-only property is the secondary target for the mouse event, if there is one.

That is:

Event name	`target`	`relatedTarget`
`mouseenter`	The `EventTarget` the pointing device entered to	The `EventTarget` the pointing device exited from
`mouseleave`	The `EventTarget` the pointing device exited from	The `EventTarget` the pointing device entered to
`mouseout`	The `EventTarget` the pointing device exited from	The `EventTarget` the pointing device entered to
`mouseover`	The `EventTarget` the pointing device entered to	The `EventTarget` the pointing device exited from
`dragenter`	The `EventTarget` the pointing device entered to	The `EventTarget` the pointing device exited from
`dragleave`	The `EventTarget` the pointing device exited from	The `EventTarget` the pointing device entered to

For events with no secondary target, relatedTarget returns null.

FocusEvent.relatedTarget is a similar property for focus events.

Value

An EventTarget object or null.

Examples

Try moving your mouse cursor into and out of the red and blue boxes.

HTML

html

<body id="body">
  <div id="outer">
    <div id="red"></div>
    <div id="blue"></div>
  </div>
  <p id="log"></p>
</body>

CSS

css

#outer {
  width: 250px;
  height: 125px;
  display: flex;
}

#red {
  flex-grow: 1;
  background: red;
}

#blue {
  flex-grow: 1;
  background: blue;
}

#log {
  max-height: 120px;
  overflow-y: scroll;
}

JavaScript

const mouseoutLog = document.getElementById("log"),
  red = document.getElementById("red"),
  blue = document.getElementById("blue");

red.addEventListener("mouseover", overListener);
red.addEventListener("mouseout", outListener);
blue.addEventListener("mouseover", overListener);
blue.addEventListener("mouseout", outListener);

function outListener(event) {
  let related = event.relatedTarget ? event.relatedTarget.id : "unknown";

  mouseoutLog.innerText = `\nfrom ${event.target.id} into ${related}${mouseoutLog.innerText}`;
}

function overListener(event) {
  let related = event.relatedTarget ? event.relatedTarget.id : "unknown";

  mouseoutLog.innerText = `\ninto ${event.target.id} from ${related}${mouseoutLog.innerText}`;
}

Result

Specifications

Specification
UI Events # dom-mouseevent-relatedtarget

Browser compatibility

	Desktop						Mobile
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	WebView Android	Chrome Android	Firefox for Android	Opera Android	Safari on IOS	Samsung Internet
`relatedTarget`	1	12	1.5	9	≤12.1	1	≤37	18	4	≤12.1	1	1.0

Docs

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