​x
 
<!DOCTYPE html>
<html>
<body>
<h1>Document 对象</h1>
​
<h2>querySelectorAll() 方法</h2>
​
<p>为所有带有 class="example" 的元素添加背景色：</p>
​
<h2 class="example">标题</h2>
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<p class="example">一个段落。</p> 
​
<script>
const nodeList = document.querySelectorAll(".example");
for (let i = 0; i < nodeList.length; i++) {
  nodeList[i].style.backgroundColor = "red";
}
</script>
​
</body>
</html>
​