The mouseenter event is fired at an Element when a pointing device (usually a mouse) is initially moved so that its hotspot is within the element at which the event was fired.

Use the event name in methods like addEventListener(), or set an event handler property.

addEventListener("mouseenter", (event) => {});

onmouseenter = (event) => {};

A MouseEvent. Inherits from Event.

This interface also inherits properties of its parents, UIEvent and Event.

MouseEvent.altKey Read only

Returns true if the alt key was down when the mouse event was fired.

MouseEvent.button Read only

The button number that was pressed (if applicable) when the mouse event was fired.

MouseEvent.buttons Read only

The buttons being pressed (if any) when the mouse event was fired.

MouseEvent.clientX Read only

The X coordinate of the mouse pointer in local (DOM content) coordinates.

MouseEvent.clientY Read only

The Y coordinate of the mouse pointer in local (DOM content) coordinates.

MouseEvent.ctrlKey Read only

Returns true if the control key was down when the mouse event was fired.

MouseEvent.layerX Non-standard Read only

Returns the horizontal coordinate of the event relative to the current layer.

MouseEvent.layerY Non-standard Read only

Returns the vertical coordinate of the event relative to the current layer.

MouseEvent.metaKey Read only

Returns true if the meta key was down when the mouse event was fired.

MouseEvent.movementX Read only

The X coordinate of the mouse pointer relative to the position of the last mousemove event.

MouseEvent.movementY Read only

The Y coordinate of the mouse pointer relative to the position of the last mousemove event.

MouseEvent.offsetX Read only

The X coordinate of the mouse pointer relative to the position of the padding edge of the target node.

MouseEvent.offsetY Read only

The Y coordinate of the mouse pointer relative to the position of the padding edge of the target node.

MouseEvent.pageX Read only

The X coordinate of the mouse pointer relative to the whole document.

MouseEvent.pageY Read only

The Y coordinate of the mouse pointer relative to the whole document.

MouseEvent.relatedTarget Read only

The secondary target for the event, if there is one.

MouseEvent.screenX Read only

The X coordinate of the mouse pointer in global (screen) coordinates.

MouseEvent.screenY Read only

The Y coordinate of the mouse pointer in global (screen) coordinates.

MouseEvent.shiftKey Read only

Returns true if the shift key was down when the mouse event was fired.

MouseEvent.mozInputSource Non-standard Read only

The type of device that generated the event (one of the MOZ_SOURCE_* constants). This lets you, for example, determine whether a mouse event was generated by an actual mouse or by a touch event (which might affect the degree of accuracy with which you interpret the coordinates associated with the event).

MouseEvent.webkitForce Non-standard Read only

The amount of pressure applied when clicking.

MouseEvent.x Read only

Alias for MouseEvent.clientX.

MouseEvent.y Read only

Alias for MouseEvent.clientY.

Though similar to mouseover, mouseenter differs in that it doesn't bubble and it isn't sent to any descendants when the pointer is moved from one of its descendants' physical space to its own physical space.

One mouseenter event is sent to each element of the hierarchy when entering them. Here 4 events are sent to the four elements of the hierarchy when the pointer reaches the text.

A single mouseover event is sent to the deepest element of the DOM tree, then it bubbles up the hierarchy until it is canceled by a handler or reaches the root.

With deep hierarchies, the number of mouseover events sent can be quite huge and cause significant performance problems. In such cases, it is better to listen for mouseenter events.

Combined with the corresponding mouseleave (which is fired at the element when the mouse exits its content area), the mouseenter event acts in a very similar way to the CSS :hover pseudo-class.

The mouseover documentation has an example illustrating the difference between mouseover and mouseenter.

The following trivial example uses the mouseenter event to change the border on the div when the mouse enters the space allotted to it. It then adds an item to the list with the number of the mouseenter or mouseleave event.

HTML

<div id="mouseTarget">
  <ul id="unorderedList">
    <li>No events yet!</li>
  </ul>
</div>

CSS

Styling the div to make it more visible.

#mouseTarget {
  box-sizing: border-box;
  width: 15rem;
  border: 1px solid #333;
}

JavaScript

let enterEventCount = 0;
let leaveEventCount = 0;
const mouseTarget = document.getElementById("mouseTarget");
const unorderedList = document.getElementById("unorderedList");

mouseTarget.addEventListener("mouseenter", (e) => {
  mouseTarget.style.border = "5px dotted orange";
  enterEventCount++;
  addListItem(`This is mouseenter event ${enterEventCount}.`);
});

mouseTarget.addEventListener("mouseleave", (e) => {
  mouseTarget.style.border = "1px solid #333";
  leaveEventCount++;
  addListItem(`This is mouseleave event ${leaveEventCount}.`);
});

function addListItem(text) {
  // Create a new text node using the supplied text
  const newTextNode = document.createTextNode(text);

  // Create a new li element
  const newListItem = document.createElement("li");

  // Add the text node to the li element
  newListItem.appendChild(newTextNode);

  // Add the newly created list item to list
  unorderedList.appendChild(newListItem);
}

• Introduction to events
• mousedown
• mouseup
• mousemove
• click
• dblclick
• mouseover
• mouseout
• mouseenter
• mouseleave
• contextmenu