<html><body><h2>按类名查找 HTML 元素</h2><p class="intro">Hello World!</p><p class="intro">Hello Sweden!</p><p class="intro">Hello Japan!</p><p id="demo"></p><script>var myElements = document.getElementsByClassName("intro");document.getElementById("demo").innerHTML = "第一段 class='intro' 是：" + myElements[0].innerHTML;</script></body></html>