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CSS Element Queries

这是 Marc J. Schmidt 创建的库的分支（链接到原始库：http://marcj.github.io/css-element-queries/），适用于使用视图封装功能的应用程序。 当前的实现允许多次调用 init() 函数，而无需每次都复制样式规则集。

Element Queries 是一个 polyfill，为所有新浏览器（包括 IE7+）添加了对基于元素的媒体查询的支持。 它不仅允许根据窗口大小定义媒体查询，还可以根据元素添加“媒体查询”功能（支持任何选择器） 大小，同时不会由于基于事件的实现而导致性能滞后。

这是一个概念验证的基于事件的 CSS 元素维度查询，具有有效的 CSS 选择器语法。

功能：

• no performance issues since it listens only on size changes of elements that have element query rules defined through css. Other element query polifills only listen on window.onresize which causes performance issues and allows only to detect changes via window.resize event and not inside layout changes like css3 animation, :hover, DOM changes etc.
• no interval/timeout detection. Truly event-based through integrated ResizeSensor class.
• automatically discovers new DOM elements. No need to call javascript manually.
• no CSS modifications. Valid CSS Syntax
• all CSS selectors available. Uses regular attribute selector. No need to write rules in HTML/JS.
• supports and tested in webkit, gecko and IE(10+)
• min-width, min-height, max-width and max-height are supported so far
• works with any layout modifications: HTML (innerHTML etc), inline styles, DOM mutation, CSS3 transitions, fluid layout changes (also percent changes), pseudo classes (:hover etc.), window resizes and more
• no Javascript-Framework dependency (works with jQuery, Mootools, etc.)
• Works beautiful for responsive images without FOUC

更多演示和信息：http://marcj.github.io/css-element-queries/

Examples

Element Query

.widget-name h2 {
    font-size: 12px;
}

.widget-name[min-width~="400px"] h2 {
    font-size: 18px;
}

.widget-name[min-width~="600px"] h2 {
    padding: 55px;
    text-align: center;
    font-size: 24px;
}

.widget-name[min-width~="700px"] h2 {
    font-size: 34px;
    color: red;
}

如您所见，我们使用 ~= 属性选择器。 因为这个 css-element-queries polyfill 在 DOM 元素上添加了新的元素属性 (

) 取决于你的实际 CSS 和元素的尺寸， 您应该始终使用此属性选择器（尤其是当您在同一元素上有多个元素查询规则时）。

<div class="widget-name">
   <h2>Element responsiveness FTW!</h2>
</div>

Responsive image

    <div data-responsive-image>
        <img data-src="http://placehold.it/350x150"/>
        <img min-width="350" data-src="http://placehold.it/700x300"/>
        <img min-width="700" data-src="http://placehold.it/1400x600"/>
    </div>

在底部包含 javascript 文件，您就可以开始了。 无需自定义 javascript 调用。

<script src="src/ResizeSensor.js"></script>
<script src="src/ElementQueries.js"></script>

See it in action:

这里是 http://marcj.github.io/css-element-queries/。

Module Loader

如果你使用的是模块加载器，你需要自己触发事件监听或初始化：

var ElementQueries = require('css-element-queries/src/ElementQueries');

 //attaches to DOMLoadContent
ElementQueries.listen();

//or if you want to trigger it yourself.
// Parse all available CSS and attach ResizeSensor to those elements which have rules attached
// (make sure this is called after 'load' event, because CSS files are not ready when domReady is fired.
ElementQueries.init();

Issues

• So far does not work on img and other elements that can't contain other elements. Wrapping with a div works fine though (See demo).
• Adds additional hidden elements into selected target element and forces target element to be relative or absolute.
• Local stylesheets do not work (using file:// protocol).
• If you have rules on an element that has a css animation, also add element-queries. E.g. .widget-name { animation: 2sec my-animation, 1s element-queries;}. We use this to detect new added DOM elements automatically.

License

麻省理工学院许可证。 版权所有 Marc J. Schmidt。