使用javascript,jQuery实现修改before,after伪类的样式（转）

<p class="red">Hello,are you kain?</p>

.red:before {
    content: ‘red‘,
    background-color  : red
}

.green:before {
    content: ‘green‘;
    background-color: green;
}

$(‘p‘).addClass(‘green‘);

document.styleSheet[0].addRule(‘.red:before‘,‘background-color:green‘);
document.styleSheet[0].insertRule(‘.red:before{background-color:green}‘,0);

var style = document.creatElement(‘style‘);
document.head.appendChild(style);
sheet = style.sheet;
sheet.addRule(‘.red:before‘,‘background-color:green‘);
sheet.insertRule(‘.red:before{background-color:green}‘,0);

// jQuery
$(‘<style>.red:before{background-color:green}</style>‘).appendTo(‘head‘);

在p标签中增加data-attr="red"属性，然后
$(‘red‘).attr(‘data-attr‘,‘green‘);