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我想通过 javascript 或 jQuery 动态更改 :before css 伪元素的 top 值...我该怎么做？
#buble{
height:70px;
width:980px;
background-color:#bce5a5;
display:none;
-moz-border-radius:5px;
-webkit-border-radius:5px;
border-radius:5px;
box-shadow:0px 0px 4px #dadada;
text-indent:35px;
color:#4a8f44;
font-weight:bold;
font-size:14pt;
}
#buble:before{
content:"";
display:block;
position:absolute;
top:77px; /* value = - border-top-width - border-bottom-width */
left:555px; /* controls horizontal position */
border-width:11px 7px 0px; /* vary these values to change the angle of the vertex */
border-style:solid;
border-color:#bce5a5 transparent;
width:0;
height:0;
}