使用js操作selected元素选中某个option
2021-05-13 22:15:48
document.getElementsByClassName()[].setAttribute("selected","")选中元素，设置selected属性
```html
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
</head>
<body>
<select name="" id="">
<option class="shanghai" value="">上海</option>
<option class="beijing" value="">北京</option>
<option class="guangzhou" value="">广州</option>
</select>
<script>
document.getElementsByClassName("guangzhou")[0].setAttribute("selected","")
</script>
</body>
</html>
```