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<html><head><meta charset="UTF-8"><title>通过按钮改变背景颜色</title><style type="text/css">*{margin: 0;padding: 0;}#top{/*background-color: blue;*/height: 400px;line-height: 400px;text-align: center;}#top button{width: 100px;height: 50px;}.red{background-color: red;}.blue{background-color: blue;}</style></head><body><div id="top" class="red"><!--点击按钮，弹出hello--><button onclick="changeColor()">改变背景颜色</button></div></body><script type="text/javascript">function changeColor(){if(document.getElementById('top').className=='blue'){document.getElementById('top').className='red'}else{document.getElementById('top').className='blue'}}</script>
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