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当定点设备(通常指鼠标)移动到元素上时就会触发 mouseenter 事件

类似 mouseover,它们两者之间的差别是 mouseenter 不会冒泡(bubble),也就是说当指针从它的子层物理空间移到它的物理空间上时不会触发

mouseenter.png
(mouseenter事件)触发时,会向层次结构的每个元素发送一个mouseenter事件。当指针到达文本时,此处将4个事件发送到层次结构的四个元素。
mouseover.png
一个单独的mouseover事件被发送到DOM树的最深层元素,然后它将层次结构向上冒泡,直到它被处理程序取消或到达根目录。

对于深层次结构,发送的mouseenter事件数量可能非常大并且会导致严重的性能问题。在这种情况下,最好是监听鼠标悬停事件。(可使用chrome开发者工具选项卡中的Performance进行性能测试)

结合其对称事件, mouseleave, mouseenter DOM事件的行为方式与CSS  :hover 伪类非常相似。.

General info

Specification
DOM L3
Interface
MouseEvent
Synchronicity
Synchronous
Bubbles
No
Cancelable
No
Target
Element
Default Action
None

Properties 属性列表

Property 属性 Type 类型 Description 描述
target 只读 EventTarget 事件(event)目标(DOM树中最顶层的目标)。
type 只读 DOMString 事件(event)类型.
bubbles 只读 Boolean Whether the event normally bubbles or not
cancelable 只读 Boolean Whether the event is cancellable or not?
view 只读 WindowProxy document.defaultView (window of the document)
detail 只读 long (float) 0.
currentTarget 只读 EventTarget The node that had the event listener attached.
relatedTarget 只读 EventTarget For mouseover, mouseout, mouseenter and mouseleave events: the target of the complementary event (the mouseleave target in the case of a mouseenter event). null otherwise.
screenX 只读 long The X coordinate of the mouse pointer in global (screen) coordinates.
screenY 只读 long The Y coordinate of the mouse pointer in global (screen) coordinates.
clientX 只读 long The X coordinate of the mouse pointer in local (DOM content) coordinates.
clientY 只读 long The Y coordinate of the mouse pointer in local (DOM content) coordinates.
button 只读 unsigned short This is always 0 as no button presses trigger this event (mouse movement does).
buttons 只读 unsigned short The buttons depressed when the mouse event was fired: Left button=1, Right button=2, Middle (wheel) button=4, 4th button (typically, "Browser Back" button)=8, 5th button (typically, "Browser Forward" button)=16. If two or more buttons are depressed, returns the logical sum of the values. E.g., if Left button and Right button are depressed, returns 3 (=1 | 2). More info.
mozPressure 只读 float The amount of pressure applied to a touch or tabdevice when generating the event; this value ranges between 0.0 (minimum pressure) and 1.0 (maximum pressure).
ctrlKey 只读 boolean true if the control key was down when the event was fired. false otherwise.
shiftKey 只读 boolean true if the shift key was down when the event was fired. false otherwise.
altKey 只读 boolean true if the alt key was down when the event was fired. false otherwise.
metaKey 只读 boolean true if the meta key was down when the event was fired. false otherwise.

Examples

鼠标悬停( mouseover )文档中有一个示例说明了mouseover和mouseenter之间的区别。

以下示例说明如何使用mouseover模拟mouseenter事件的事件委派原则。

<ul id="test">
  <li>
    <ul class="enter-sensitive">
      <li>item 1-1</li>
      <li>item 1-2</li>
    </ul>
  </li>
  <li>
    <ul class="enter-sensitive">
      <li>item 2-1</li>
      <li>item 2-2</li>
    </ul>
  </li>
</ul>

<script>
  var delegationSelector = ".enter-sensitive";

  document.getElementById("test").addEventListener("mouseover", function( event ) {
    var target = event.target,
        related = event.relatedTarget,
        match;

    // search for a parent node matching the delegation selector
    while ( target && target != document && !( match = matches( target, delegationSelector ) ) ) {
        target = target.parentNode;
    }

    // exit if no matching node has been found
    if ( !match ) { return; }

    // loop through the parent of the related target to make sure that it's not a child of the target
    while ( related && related != target && related != document ) {
        related = related.parentNode;
    }

    // exit if this is the case
    if ( related == target ) { return; }

    // the "delegated mouseenter" handler can now be executed
    // change the color of the text
    target.style.color = "orange";
    // reset the color after a small amount of time
    setTimeout(function() {
        target.style.color = "";
    }, 500);
    

  }, false);
 

  // function used to check if a DOM element matches a given selector
  // the following code can be replaced by this IE8 compatible function: https://gist.github.com/2851541
  function matches( elem, selector ){
    // the webkitMatchesSelector is prefixed in most (if not all) browsers
    return elem.webkitMatchesSelector( selector );
  };
</script>

Browser compatibility

We're converting our compatibility data into a machine-readable JSON format. This compatibility table still uses the old format, because we haven't yet converted the data it contains. Find out how you can help!

Feature Chrome Edge Firefox (Gecko) Internet Explorer Opera Safari
Basic support 30[1] (Yes) 10[2] 5.5 (Yes)
未实现 15.0
17.0
7[3]
On disabled form elements 未实现 未实现 44.0 (44.0)[4] 未实现 未实现 ?
Feature Android Chrome for Android Edge Firefox Mobile (Gecko) IE Mobile Opera Mobile Safari Mobile
Basic support ? ? (Yes) ? ? ? ?
On disabled form elements ? ? 未实现 ? ? ? ?

[1] Implemented in bug 236215.

[2] Implemented in bug 432698.

[3] Safari 7 fires the event in many situations where it's not allowed to, making the whole event useless. See bug 470258 for the description of the bug (it existed in old Chrome versions as well). Safari 8 has correct behavior

[4] Implemented in bug 218093.

See also

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此页面的贡献者: irenesmith, fscholz, littleostar, winson
最后编辑者: fscholz,