问题遇到的现象和发生背景
问题相关代码，请勿粘贴截图
运行结果及报错内容
我的解答思路和尝试过的方法
我想要达到的结果
<!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>
<style>
.main .listOne li {
background-color: bisque;
}
.main .spanList span {
background-color: rgb(150, 232, 62);
}
.main .divList div {
background-color: rgb(38, 58, 209);
}
</style>
</head>
<body>
<div class="main">
<ol class="listOne">
<li>oneli</li>
<li>oneli</li>
<li>oneli</li>
<li>oneli</li>
<li>oneli</li>
</ol>
<div class="spanList">
<span>spanOne</span><br>
<span>spanOne</span><br>
<span>spanOne</span><br>
<span>spanOne</span><br>
<span>spanOne</span><br>
</div>
<div class="divList">
<div>divOne</div>
<div>divOne</div>
<div>divOne</div>
<div>divOne</div>
<div>divOne</div>
</div>
</div>
<script>
var liListOne = document.getElementsByClassName(".listOne");
var allEl = document.querySelectorAll('.main');
console.log(allEl);
var arrLi = liListOne[0];
console.log(liListOne);
var a = allEl.classList;
console.log(a);
</script>
</body>
</html>
