效果：js

<div id="append">ss</div>
<script>
var divA = document.getElementById("append");
    divA.innerHTML = divA.innerText+'追加的內容s';
    //divA.innerHTML +='追加的內容s';
    divA.innerHTML = divA.innerHTML+'<h3>追加內容為H3字型</h3>';
</script>

效果：jq

<div id="append">
  <span>文字</span>
  <p>This is a paragraph.</p>
  <ol>
  <li>List item 1</li>
  </ol>
</div>
<script>
$(document).ready(function(){
    $('span').append('隨便加文字');//無效果
    $("p").append(" <b>Appended text</b>.");//有標籤效果
    $("ol").append("<li>Appended item</li>");
});
</script>
 

<p>This is a paragraph.</p>
<p>This is a paragraph.</p>
<script type="text/javascript">
$(document).ready(function(){
    $("p:first-child").html("Hello <b>world!</b>");//替換裡面的所以內容  $("p").eq(0).html("Hello <b>world!</b>")第一個p
});
</script>