html – 当页面高度使用CSS动态更改时,将页脚保持在页面底部

问题是页面可以动态地改变它的高度.

使用the current solution I’m using,页脚位于页面底部.但是当页面高度动态变化时,页脚将保持在其确切位置.

页脚的CSS如下：

#footer {
    position: absolute;
    right: 0;
    bottom: 0;
    left: 0;
}

html和body标签具有以下规则：

html,body {
    min-height: 100%;
    height: 100%;
}

请参阅下面的代码段以获取可视化演示(最适合在全窗口模式下使用)

$(document).ready(function() {
  
  var button = $("#addContent");
  var lorem = "<p>Proin cursus odio quis neque porttitor pretium. Duis cursus dolor mi,quis blandit eros Dictum vitae. Mauris tempus turpis non Leo commodo sagittis ac ac urna. Vivamus aliquet euismod posuere. Suspendisse at semper mauris. Phasellus blandit convallis Tincidunt. Maecenas elementum ullamcorper risus,a vestibulum ex accumsan sed. Nulla facilisi.</p><p>Proin cursus odio quis neque porttitor pretium. Duis cursus dolor mi,a vestibulum ex accumsan sed. Nulla facilisi.</p>";
  
  button.click(function() {
    
    $("main button").before(lorem);
    
  });
  
});

* {
  box-sizing: border-box;
}

body {
  margin: 0;
}

header {
  BACkground: #333;
  color: #fff;
  padding: 25px;
}

main {
  padding: 25px;
}

main h3 {
  margin-top: 0;
}

code {
  BACkground: #f1f1f1;
  padding: 0 5px;
}

footer {
  position: absolute;
  BACkground: #ededed;
  padding: 25px;
  color: #000;
  right: 0;
  bottom: 0;
  left: 0;
}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>

<header>
  <p>Just a sample header</p>
</header>

<main>
  <h3>Some sample content</h3>
  <p>Click on the <code>button</code> to see what i mean.</p>
  <p>When the <code>heigth</code> of the page dynamically changes,the <code>footer</code> will stay at its exact position.</p>
  <button id="addContent">Click to add more content</button>
</main>

<footer>
  <p>The footer</p>
</footer>

如何让CSS知道高度变化？并将该页脚保留在文档的底部而不是它停留在窗口的底部？