docs(cn): translate content/docs/reference-dom-elements.md into Chinese (reactjs#105)

Author: zbc

content/docs/reference-dom-elements.md

@@ -1,6 +1,6 @@
 ---
 id: dom-elements
-title: DOM Elements
+title: DOM 元素
 layout: docs
 category: Reference
 permalink: docs/dom-elements.html
@@ -14,27 +14,27 @@ redirect_from:
   - "tips/dangerously-set-inner-html.html"
 ---
 
-React implements a browser-independent DOM system for performance and cross-browser compatibility. We took the opportunity to clean up a few rough edges in browser DOM implementations.
+React 实现了一套独立于浏览器的 DOM 系统，兼顾了性能和跨浏览器的兼容性。我们借此机会完善了浏览器 DOM 实现的一些特殊情况。
 
-In React, all DOM properties and attributes (including event handlers) should be camelCased. For example, the HTML attribute `tabindex` corresponds to the attribute `tabIndex` in React. The exception is `aria-*` and `data-*` attributes, which should be lowercased. For example, you can keep `aria-label` as `aria-label`.
+在 React 中，所有的 DOM 特性和属性（包括事件处理）都应该是小驼峰命名的方式。例如，与 HTML 中的 `tabindex` 属性对应的 React 的属性是 `tabIndex`。例外的情况是 `aria-*` 以及 `data-*` 属性，一律使用小写字母命名。比如, 你依然可以用 `aria-label` 作为 `aria-label`。
 
-## Differences In Attributes {#differences-in-attributes}
+## 属性差异 {#differences-in-attributes}
 
-There are a number of attributes that work differently between React and HTML:
+React 与 HTML 之间有很多属性存在差异：
 
 ### checked {#checked}
 
-The `checked` attribute is supported by `<input>` components of type `checkbox` or `radio`. You can use it to set whether the component is checked. This is useful for building controlled components. `defaultChecked` is the uncontrolled equivalent, which sets whether the component is checked when it is first mounted.
+当 `<input>` 组件的 type 类型为 `checkbox` 或 `radio` 时，组件支持 `checked` 属性。你可以使用它来设置组件是否被选中。这对于构建受控组件（controlled components）很有帮助。而 `defaultChecked` 则是非受控组件的属性，用于设置组件首次挂载时是否被选中。
 
 ### className {#classname}
 
-To specify a CSS class, use the `className` attribute. This applies to all regular DOM and SVG elements like `<div>`, `<a>`, and others.
+`className` 属性用于指定 CSS 的 class，此特性适用于所有常规 DOM 节点和 SVG 元素，如 `<div>`，`<a>` 及其它标签。
 
-If you use React with Web Components (which is uncommon), use the `class` attribute instead.
+如果你在 React 中使用 Web Components（这是一种不常见的使用方式），请使用 class 属性代替。
 
 ### dangerouslySetInnerHTML {#dangerouslysetinnerhtml}
 
-`dangerouslySetInnerHTML` is React's replacement for using `innerHTML` in the browser DOM. In general, setting HTML from code is risky because it's easy to inadvertently expose your users to a [cross-site scripting (XSS)](https://en.wikipedia.org/wiki/Cross-site_scripting) attack. So, you can set HTML directly from React, but you have to type out `dangerouslySetInnerHTML` and pass an object with a `__html` key, to remind yourself that it's dangerous. For example:
+`dangerouslySetInnerHTML` 是 React 为浏览器 DOM 提供 `innerHTML` 的替换方案。通常来讲，使用代码直接设置 HTML 存在风险，因为很容易无意中使用户暴露于[跨站脚本（XSS）](https://en.wikipedia.org/wiki/Cross-site_scripting)的攻击。因此，你可以直接在 React 中设置 HTML，但当你想设置 `dangerouslySetInnerHTML` 时，需要向其传递包含 key 为 `__html` 的对象，以此来警示你。例如：
 
 ```js
 function createMarkup() {
@@ -48,23 +48,23 @@ function MyComponent() {
 
 ### htmlFor {#htmlfor}
 
-Since `for` is a reserved word in JavaScript, React elements use `htmlFor` instead.
+由于 `for` 在 JavaScript 中是保留字，所以 React 元素中使用了 `htmlFor` 来代替。
 
 ### onChange {#onchange}
 
-The `onChange` event behaves as you would expect it to: whenever a form field is changed, this event is fired. We intentionally do not use the existing browser behavior because `onChange` is a misnomer for its behavior and React relies on this event to handle user input in real time.
+`onChange` 事件与预期行为一致：每当表单字段变化时，该事件都会被触发。我们故意没有使用浏览器已有的默认行为，是因为 `onChange` 在浏览器中的行为和名称不对应，并且 React 依靠了该事件实时处理用户输入。
 
 ### selected {#selected}
 
-The `selected` attribute is supported by `<option>` components. You can use it to set whether the component is selected. This is useful for building controlled components.
+`<option>` 组件支持 `selected` 属性。你可以使用该属性设置组件是否被选择。这对构建受控组件很有帮助。
 
 ### style {#style}
 
->Note
+>注意
 >
->Some examples in the documentation use `style` for convenience, but **using the `style` attribute as the primary means of styling elements is generally not recommended.** In most cases, [`className`](#classname) should be used to reference classes defined in an external CSS stylesheet. `style` is most often used in React applications to add dynamically-computed styles at render time. See also [FAQ: Styling and CSS](/docs/faq-styling.html).
+>在文档中，部分例子为了方便，直接使用了 `style`，但是**通常不推荐将 `style` 属性作为设置元素样式的主要方式**。在多数情况下，应使用 [`className`](#classname) 属性来引用外部 CSS 样式表中定义的 class。`style` 在 React 应用中多用于在渲染过程中添加动态计算的样式。另请参阅：[FAQ：Styling 和 CSS](/docs/faq-styling.html)。
 
-The `style` attribute accepts a JavaScript object with camelCased properties rather than a CSS string. This is consistent with the DOM `style` JavaScript property, is more efficient, and prevents XSS security holes. For example:
+`style` 接受一个采用小驼峰命名属性的 JavaScript 对象，而不是 CSS 字符串。这与 DOM 中 `style` 的 JavaScript 属性是一致的，同时会更高效的，且能预防跨站脚本（XSS）的安全漏洞。例如：
 
 ```js
 const divStyle = {
@@ -77,7 +77,7 @@ function HelloWorldComponent() {
 }
 ```
 
-Note that styles are not autoprefixed. To support older browsers, you need to supply corresponding style properties:
+注意：样式不会自动补齐前缀。如需支持旧版浏览器，请手动补充对应的样式属性：
 
 ```js
 const divStyle = {
@@ -90,9 +90,9 @@ function ComponentWithTransition() {
 }
 ```
 
-Style keys are camelCased in order to be consistent with accessing the properties on DOM nodes from JS (e.g. `node.style.backgroundImage`). Vendor prefixes [other than `ms`](https://www.andismith.com/blogs/2012/02/modernizr-prefixed/) should begin with a capital letter. This is why `WebkitTransition` has an uppercase "W".
+Style 中的 key 采用小驼峰命名是为了与 JS 访问 DOM 节点的属性保持一致（例如：`node.style.backgroundImage` ）。浏览器引擎前缀都应以大写字母开头，[除了 `ms`](https://www.andismith.com/blog/2012/02/modernizr-prefixed/)。因此，`WebkitTransition` 首字母为 ”W”。
 
-React will automatically append a "px" suffix to certain numeric inline style properties. If you want to use units other than "px", specify the value as a string with the desired unit. For example:
+React 会自动添加 ”px” 后缀到内联样式为数字的属性后。如需使用 ”px” 以外的单位，请将此值设为数字与所需单位组成的字符串。例如：
 
 ```js
 // Result style: '10px'
@@ -106,37 +106,37 @@ React will automatically append a "px" suffix to certain numeric inline style pr
 </div>
 ```
 
-Not all style properties are converted to pixel strings though. Certain ones remain unitless (eg `zoom`, `order`, `flex`). A complete list of unitless properties can be seen [here](https://github.com/facebook/react/blob/4131af3e4bf52f3a003537ec95a1655147c81270/src/renderers/dom/shared/CSSProperty.js#L15-L59).
+但并非所有样式属性都转换为像素字符串。有些样式属性是没有单位的(例如 `zoom`，`order`，`flex`)。无单位属性的完整列表在[此处](https://github.com/facebook/react/blob/4131af3e4bf52f3a003537ec95a1655147c81270/src/renderers/dom/shared/CSSProperty.js#L15-L59)。
 
 ### suppressContentEditableWarning {#suppresscontenteditablewarning}
 
-Normally, there is a warning when an element with children is also marked as `contentEditable`, because it won't work. This attribute suppresses that warning. Don't use this unless you are building a library like [Draft.js](https://facebook.github.io/draft-js/) that manages `contentEditable` manually.
+通常，当拥有子节点的元素被标记为 `contentEditable` 时，React 会发出一个警告，因为这不会生效。此属性会触发警告信息。尽量不要使用该属性，除非你要构建一个类似 [Draft.js](https://facebook.github.io/draft-js/) 的手动管理 `contentEditable` 属性的库。
 
 ### suppressHydrationWarning {#suppresshydrationwarning}
 
-If you use server-side React rendering, normally there is a warning when the server and the client render different content. However, in some rare cases, it is very hard or impossible to guarantee an exact match. For example, timestamps are expected to differ on the server and on the client.
+如果你使用 React 服务端渲染，通常会在当服务端与客户端渲染不同的内容时发出警告。但是，在一些极少数的情况下，很难甚至于不可能保证内容的一致性。例如，在服务端和客户端上，时间戳通常是不同的。 
 
-If you set `suppressHydrationWarning` to `true`, React will not warn you about mismatches in the attributes and the content of that element. It only works one level deep, and is intended to be used as an escape hatch. Don't overuse it. You can read more about hydration in the [`ReactDOM.hydrate()` documentation](/docs/react-dom.html#hydrate).
+如果设置 `suppressHydrationWarning` 为 `true`，React 将不会警告你属性与元素内容不一致。它只会对元素一级深度有效，并且打算作为应急方案。因此不要过度使用它。你可以在 [`ReactDOM.hydrate()` 文档](/docs/react-dom.html#hydrate) 中了解更多关于 hydration 的信息。
 
 ### value {#value}
 
-The `value` attribute is supported by `<input>` and `<textarea>` components. You can use it to set the value of the component. This is useful for building controlled components. `defaultValue` is the uncontrolled equivalent, which sets the value of the component when it is first mounted.
+`<input>` 和 `<textarea>` 组件支持 `value` 属性。你可以使用它为组件设置 value。这对于构建受控组件是非常有帮助。`defaultValue` 属性对应的是非受控组件的属性，用于设置组件第一次挂载时的 value。
 
 ## All Supported HTML Attributes {#all-supported-html-attributes}
 
-As of React 16, any standard [or custom](/blog/2017/09/08/dom-attributes-in-react-16.html) DOM attributes are fully supported.
+在 React 16 中，任何标准的[或自定义的](/blog/2017/09/08/dom-attributes-in-react-16.html) DOM 属性都是完全支持的。
 
-React has always provided a JavaScript-centric API to the DOM. Since React components often take both custom and DOM-related props, React uses the `camelCase` convention just like the DOM APIs:
+React 为 DOM 提供了一套以 JavaScript 为中心的 API。由于 React 组件经常采用自定义或和 DOM 相关的 props 的关系，React 采用了`小驼峰命名`的方式，正如 DOM APIs 那样：
 
 ```js
 <div tabIndex="-1" />      // Just like node.tabIndex DOM API
 <div className="Button" /> // Just like node.className DOM API
 <input readOnly={true} />  // Just like node.readOnly DOM API
 ```
 
-These props work similarly to the corresponding HTML attributes, with the exception of the special cases documented above.
+除了上述文档提到的特殊拼写方式以外，这些 props 的用法与 HTML 的属性也极为类似。
 
-Some of the DOM attributes supported by React include:
+React 支持的 DOM 属性有：
 
 ```
 accept acceptCharset accessKey action allowFullScreen alt async autoComplete
@@ -154,7 +154,7 @@ sizes span spellCheck src srcDoc srcLang srcSet start step style summary
 tabIndex target title type useMap value width wmode wrap
 ```
 
-Similarly, all SVG attributes are fully supported:
+同样，所有的 SVG 属性也完全得到了支持：
 
 ```
 accentHeight accumulate additive alignmentBaseline allowReorder alphabetic
@@ -193,4 +193,4 @@ xlinkHref xlinkRole xlinkShow xlinkTitle xlinkType xmlns xmlnsXlink xmlBase
 xmlLang xmlSpace y y1 y2 yChannelSelector z zoomAndPan
 ```
 
-You may also use custom attributes as long as they're fully lowercase.
+你也可以使用自定义属性，但要注意属性名全都为小写。