<script src="js/jquery-1.8.3.min.js"></script>

<script>

window.onload=function(){

if (screen.width <= 1024){ //分辨率小于等于1024时

$(".m1").attr("class", "red");//替换class为ml的样式为red;

$(".m2").show();

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$(".m1").show();

$(".m2").hide();

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}

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<style>

.red {color:red;}

</style>

</head>


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<div class="m2">m2m2m2m2m2m2m2m2mm2m2m2m2m2m</div>

</body>