返回值:jQuerymouseover(handler(eventObject))

Bind an event handler to the "mouseover" JavaScript event, or trigger that event on an element.

This method is a shortcut for .bind('mouseover', handler) in the first variation, and .trigger('mouseover') in the second.

The mouseover event is sent to an element when the mouse pointer enters the element. Any HTML element can receive this event.

For example, consider the HTML:

<div id="outer">
  Outer
  <div id="inner">
    Inner
  </div>
</div>
<div id="other">
  Trigger the handler
</div>
<div id="log"></div>

The event handler can be bound to any element:

$('#outer').mouseover(function() {
  $('#log').append('<div>Handler for .mouseover() called.</div>');
});

Now when the mouse pointer moves over the Outer <div>, the message is appended to <div id="log">. We can also trigger the event when another element is clicked: 

$('#other').click(function() {
  $('#outer').mouseover();
});

After this code executes, clicks on Trigger the handler will also append the message.

This event type can cause many headaches due to event bubbling. For instance, when the mouse pointer moves over the Inner element in this example, a mouseover event will be sent to that, then trickle up to Outer. This can trigger our bound mouseover handler at inopportune times. See the discussion for .mouseenter() for a useful alternative.

示例:

Show the number of times mouseover and mouseenter events are triggered. mouseover fires when the pointer moves into the child element as well, while mouseenter fires only when the pointer moves into the bound element. 

<!DOCTYPE html>
<html>
<head>
<style>
div.out { width:40%; height:120px; margin:0 15px;
          background-color:#D6EDFC; float:left; }
div.in {  width:60%; height:60%; 
          background-color:#FFCC00; margin:10px auto; }
p { line-height:1em; margin:0; padding:0; }
</style>
<script src="jquery.min.js"></script>
</head>
<body>


<div class="out overout">
  <span>move your mouse</span>
  <div class="in">
  </div>
</div>

<div class="out enterleave">
  <span>move your mouse</span>
  <div class="in">
  </div>
</div>


<script>


  var i = 0;
  $("div.overout").mouseover(function() {
    i += 1;
    $(this).find("span").text( "mouse over x " + i );
  }).mouseout(function(){
    $(this).find("span").text("mouse out ");
  });

  var n = 0;
  $("div.enterleave").mouseenter(function() {
    n += 1;
    $(this).find("span").text( "mouse enter x " + n );
  }).mouseleave(function() {
    $(this).find("span").text("mouse leave");
  });



</script>
</body>
</html>
演示: