关于javascript获取内联样式与嵌入式样式的实例

通过style属性设置背景图案

<!--html-->
<div id="change">
change color
</div>

/*css*/
#change {
      border: 1px solid black;
      width: 200px;
      height: 200px;
      text-align: center;
      line-height: 200px;
    }

//js
change.style.backgroundColor="purple";

在侧边栏设置一个颜色选择器，将change的背景颜色设置为选择的颜色，此时颜色选择器的颜色是使用内联样式的方式添加的。

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>css</title>
  <style>
    * {
      margin: 0;
      padding: 0;
    }

    .wrap {
      width: 220px;
      height: 200px;
      position: absolute;
      top: 300px;
      left: -172px;
    }

    .open-close {
      height: 45px;
      width: 48px;
      background: url("open-close.png") no-repeat;
      background-size: contain;
      border: 1px solid grey;
      border-left: none;
      position: absolute;
      top: 0;
      right: 0;
      z-index: 2;
    }

    .changer {
      height: 150px;
      width: 170px;
      position: absolute;
      top: 0;
      left: 0;
      border: 1px solid grey;
      text-align: center;
      padding-top: 8px;
    }

    .list > li {
      display: block;
      width: 36px;
      height: 36px;
      float: left;
      margin-left: 9%;
      margin-top: 10%;
    }

    #change {
      border: 1px solid black;
      width: 200px;
      height: 200px;
      text-align: center;
      line-height: 200px;
    }
  </style>
</head>
<body>
<div class="wrap" id="wrap">
  <!--html-->
  <div class="open-close" id="open"></div>
  <div class="changer">
    <span>颜色选择器</span>
    <ul class="list">
      <li class="color-orange" style="background-color: orange"></li>
      <li class="color-red" style="background-color: red"></li>
      <li class="color-blue" style="background-color: blue"></li>
      <li class="color-black" style="background-color: black"></li>
      <li class="color-green" style="background-color: green"></li>
      <li class="color-pink" style="background-color: pink"></li>
    </ul>
  </div>
</div>
<div id="change">
  change color
</div>
<script>
  var open = document.getElementById("open");
  var wrap = document.getElementById("wrap");
  var list = document.getElementById("list");
  var change = document.getElementById("change");
  var color_change = document.getElementsByTagName("li");
  change.style.backgroundColor = "purple";
  open.onmouseover = function () {
    wrap.style.left = 0 + "px";

  };
  open.onclick = function () {
    wrap.style.left = -172 + "px";
  };
  for (var i = 0; i < color_change.length; i++) {
    color_change[i].id = i;
    color_change[i].onclick = function () {
      change.style.backgroundColor = color_change[this.id].style.backgroundColor;
    }
  }
</script>
</body>
</html>

问题：

当颜色选择器的颜色是使用嵌入式或者外部引入的方式添加时，javascript的style属性无效，获取不到颜色值。

解决方法：

javascript的style属性只能获取内联样式，对于外部引入样式和嵌入式样式需要用currentStyle属性。但是，currentStyle在Firefox和Chrome下不支持，需要使用如下兼容性代码:

HTMLElement.prototype.__defineGetter__("currentStyle", function () {
      return this.ownerDocument.defaultView.getComputedStyle(this, null);
    });

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Title</title>
  <style>
    * {
      margin: 0;
      padding: 0;
    }
    .wrap {
      width: 220px;
      height: 200px;
      position: absolute;
      top: 300px;
      left: -172px;
    }
    .open-close {
      height: 45px;
      width: 48px;
      background: url("open-close.png") no-repeat;
      background-size: contain;
      border: 1px solid grey;
      border-left: none;
      position: absolute;
      top: 0;
      right: 0;
      z-index: 2;
    }
    .changer {
      height: 150px;
      width: 170px;
      position: absolute;
      top: 0;
      left: 0;
      border: 1px solid grey;
      text-align: center;
      padding-top: 8px;
    }
    .list > li {
      display: block;
      width: 36px;
      height: 36px;
      float: left;
      margin-left: 9%;
      margin-top: 10%;
    }
    .color-orange {
      background-color: orange;
    }
    .color-red {
      background-color: red;
    }
    .color-blue {
      background-color: blue;
    }
    .color-blank {
      background-color: black;
    }
    .color-green {
      background-color: green;
    }
    .color-pink {
      background-color: pink;
    }
    #change {
      border: 1px solid black;
      width: 200px;
      height: 200px;
      text-align: center;
      line-height: 200px;
    }
  </style>
</head>
<body>
<div class="wrap" id="wrap">
  <!--html-->
  <div class="open-close" id="open"></div>
  <div class="changer">
    <span>颜色的选择</span>
    <ul class="list">
      <li class="color-orange"></li>
      <li class="color-red"></li>
      <li class="color-blue"></li>
      <li class="color-blank"></li>
      <li class="color-green"></li>
      <li class="color-pink"></li>
    </ul>
  </div>
</div>
<div id="change">
change color
</div>
<script>
  HTMLElement.prototype.__defineGetter__("currentStyle", function () {
    return this.ownerDocument.defaultView.getComputedStyle(this, null);
  });
  var open = document.getElementById("open");
  var wrap = document.getElementById("wrap");
  var list = document.getElementById("list");
  var change = document.getElementById("change");
  var color_change = document.getElementsByTagName("li");
  change.style.backgroundColor="purple";
  open.onmouseover = function () {
    wrap.style.left = 0 + "px";

  };
  open.onclick = function () {
    wrap.style.left = -172 + "px";
  };

  for (var i = 0; i < color_change.length; i++) {
    color_change[i].id = i;
    color_change[i].onclick = function () {
      change.style.backgroundColor = color_change[this.id].currentStyle.backgroundColor;
    }
  }
</script>
</body>
</html>

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