<input type="button" value="动起来" id="btn" />
    <div id="div1" style="width:100.5px; height: 100px; background: red; position: absolute; left: 100px; top: 30px;"></div>
    <div style="width:100px; height: 100px; background: black; position: absolute; left:100px; top: 120px; "></div>

js代码：

window.onload = function() {
    var oBtn = document.getElementById('btn');
    var oDiv = document.getElementById('div1');
    alert( oDiv.offsetWidth );//四舍五入运算
}

经由过程试验我们发明，款式能够设置为小数，然则js获取其值的时刻，会举行四舍五入。