jquery------使用jQuery的委托方法

index.jsp

<div id="gallery">
        <div class="photo">
            <img src="addimage/p1.jpg">
            <div class="details">
                <div class="author">Me</div>
                <div class="date">2016/5/22</div>
            </div>
        </div>
        <div class="photo">
            <img src="addimage/p2.jpg">
            <div class="details">
                <div class="author">Me</div>
                <div class="date">2016/5/23</div>
            </div>
        </div>
        <div class="photo">
            <img src="addimage/p3.jpg">
            <div class="details">
                <div class="author">Me</div>
                <div class="date">2016/5/24</div>
            </div>
        </div>
    </div>

my.js

$(document).ready(function(){
    /*$("div.photo").each(function(index){
        $(this).hover(function(){
            var $left=$(this).offset().left+120;
            var $top=$(this).offset().top-150;
            $(this).find(".details").fadeTo(1000,1.0).css({left:$left,top:$top,});
            $(this).fadeTo(1000,0.5);
        },function(){
            $(this).find(".details").fadeTo(1000,0);
            $(this).fadeTo(200,1.0);
        });
    });*/

    /*$("div.photo").on("mouseenter mouseleave",function(event){
        var $details=$(this).find(".details");
        var $left=$(this).offset().left+120;
        var $top=$(this).offset().top-150;
        if(event.type=="mouseenter"){
            $details.toggleClass("showtime",event.type=="mouseenter");
            $details.fadeTo(1000,1.0).css({left:$left,top:$top,});
            $(this).fadeTo(1000,0.5);
        }
        else{
            $details.fadeOut("fast");
            $(this).fadeTo(200,1.0);
        }
    });*/

    //jquery中的事件委托
    $("#gallery").on("mouseenter mouseleave","div.photo",function(event){
        var $details=$(this).find(".details");//this是div.photo
        var $top=$("div.photo").offset().top-30;
        var $left=$details.closest("div.photo").offset().left+220;
        if(event.type=="mouseenter"){
            $details.fadeTo("fast",1.0).css({top:$top,left:$left});
            $details.closest("div.photo").find("img").css({opacity:0.5});
        }
        else{
            $details.fadeOut("fast");
            $details.closest("div.photo").find("img").css({opacity:1.0});
        }
    });

});

css.css

.photo{
    display:inline;
}
img{
    width:300px;
    height:200px;
}
.details{
    position:absolute;
    display:none;
    color:#fff;
}
.showtime{
    border:2px solid #aaa;
}