previousSibling是上一个节点或null,包括文本节点
previousElementSibling是上一个元素节点或null,不包括文本节点
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
</head>
<body>
<div>
<div>first div</div>
我是文本节点
<div id="haha"></div>
</div>
<script>
console.log(haha.previousSibling)
console.log(haha.previousElementSibling)
</script>
</body>
</html>
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