基于jQuery加载进度条特效代码

<div id="main">
    <div class="demo">
        <div class="bars">
            <span id="bar">55</span>
        </div>
        <div class="bars">
            <span id="bar2">75</span>
        </div>
        <div class="bars">
            <span id="bar3">25</span>
        </div>
        <div class="bars">
            <span id="bar4">45</span>
            <p><button id="load">加载新数据</button> <button id="get">获取数据</button></p>
        </div>
    </div>
</div>