js实现动态打字效果

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <title>WriteFont</title>
  </head>
  <body>
    <div id="divTyping"></div>

    <script type="text/javascript">
      var str = "<big>我现在根本不想上什么晚课,<br><br>只想早点为祖国庆生!";
      var i = 0;
      function typing() {
        var divTyping = document.getElementById("divTyping");
        if (i <= str.length) {
          divTyping.innerHTML = str.slice(0, i++) + "_";
          setTimeout("typing()", 300); //每2s调用一次typing()
        } else {
          divTyping.innerHTML = str; //结束打字,移除_光标
        }
      }
      typing();
    </script>
  </body>
</html>