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HTML Settings

Here you can Sed posuere consectetur est at lobortis. Donec ullamcorper nulla non metus auctor fringilla. Maecenas sed diam eget risus varius blandit sit amet non magna. Donec id elit non mi porta gravida at eget metus. Praesent commodo cursus magna, vel scelerisque nisl consectetur et.

            矢量图: 例如svg,一般不需要自身尺寸和自身比例。如果有,那么一定是既有自身尺寸,又有自身比例
            element: 拥有element元素的尺寸和比例
<p>下面示例:图片尺寸: 700 x 466 容器尺寸: 800 x 500</p>
<div class="area">
                contain: 最大限度填充背景区域,但是不能被裁剪,因此例子中的图片会适应高度放大
                cover: 填满背景容器区域,图片可以被裁剪,因此例子中的图片会适应宽度放大
                auto: 如果图片有自身尺寸,则按照自身尺寸展示,可以看到下面的例子中图片不会撑满容器
    <select name="one" id="one">
            <option value="contain">contain</option>
            <option value="cover">cover</option>
            <option value="auto" selected>auto</option>
    <div class="display" id="oneDisplay"></div>
<div class="area">
    <input type="text" class="two-value" id="twoValue">
    <div class="display" id="twoDisplay1"></div>
<div class="area">
    <input type="text" class="two-value" id="twoValue1">
    <input type="text" class="two-value" id="twoValue2">
    <div class="display" id="twoDisplay2"></div>
              pre {
    white-space: pre-line;
.area {
    margin-right: 20px;
    margin-bottom: 20px;
.display {
    margin-top: 10px;
    border: 1px dotted darkblue;
    width: 800px;
    height: 500px;
    background: url("http://p0xmvstv1.bkt.clouddn.com/css/background/ylj.jpeg") no-repeat;

              var one = document.querySelector("#one");
var twoValue = document.querySelector("#twoValue");
var twoValue1 = document.querySelector("#twoValue1");
var twoValue2 = document.querySelector("#twoValue2");

var oneDisplay = document.querySelector("#oneDisplay");
var twoDisplay1 = document.querySelector("#twoDisplay1");
var twoDisplay2 = document.querySelector("#twoDisplay2");

one.addEventListener("change", function(e) {
    var value = e.target.value;
    oneDisplay.style.backgroundSize = value;

twoValue.addEventListener("change", function(e) {
    var value = e.target.value;
    twoDisplay1.style.backgroundSize = "auto " + value;

twoValue1.addEventListener("change", function(e) {
    var value = e.target.value;
    var value2 = twoValue2.value;
    twoDisplay2.style.backgroundSize = value + " " + value2;

twoValue2.addEventListener("change", function(e) {
    var value = e.target.value;
    var value1 = twoValue1.value;
    twoDisplay2.style.backgroundSize = value1 + " " + value;

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