效果图
结构
<div class="box" style="width:200px"></div>
CSS
.box {
width: 200px;
height: 200px;
background-color: pink;
padding: 10px;
}
JS
// offset 与style的区别
var box = document.querySelector('.box');
console.log(box.offsetWidth);
console.log(box.style.width);
box.style.width = '300px';
// 获取大小用offset 给值用style