//while循环 <script type="text/javascript">i = 1;while (i <= 6){document.write("<h" + i+">这是标题"+i);document.write("</h"+i+">");i++;}</script>

 //do_whilel循环<script type="text/javascript">i = 1;do{document.write("<h" + i+">这是标题"+i);document.write("</h"+i+">");i++;}while(i<=6);</script>

//for循环  <script type="text/javascript">for(i=1;i<=6;i++){  document.write("<h"+i+">这是标题"+i);  document.write("</h"+i+">");}</script>