在您的示例中，您可以使用：

In your example you can use:

/
  <h   // Match literal <h
  (.)  // Match any character and save in a group
  >    // Match literal <
  .*?  // Match any character zero or more times, non greedy
  <\/h // Match literal </h
  \1   // Match what previous grouped in (.)
  >    // Match literal >
/g

var str = '<h1>A</h1><h2>B</h2><p>Foobar</p><h3>C</h3>'
str.match(/<h(.)>.*?<\/h\1>/g); // ["<h1>A</h1>", "<h2>B</h2>", "<h3>C</h3>"]

但请不要使用regexp解析HTML，请阅读 RegEx匹配除XHTML自包含标签之外的开放标签

But please don't parse HTML with regexp, read RegEx match open tags except XHTML self-contained tags