docs(cn): translate content/docs/portals.md into Chinese (#147)

zbc · QC-L · commit 0cbc2d492eb6 · 2019-04-12T11:16:22.000+08:00
diff --git a/content/docs/portals.md b/content/docs/portals.md
@@ -4,21 +4,21 @@ title: Portals
 permalink: docs/portals.html
 ---
 
-Portals provide a first-class way to render children into a DOM node that exists outside the DOM hierarchy of the parent component.
+Portal 提供了一种将子节点渲染到存在于父组件以外的 DOM 节点的优秀的方案。
 
 ```js
 ReactDOM.createPortal(child, container)
 ```
 
-The first argument (`child`) is any [renderable React child](/docs/react-component.html#render), such as an element, string, or fragment. The second argument (`container`) is a DOM element.
+第一个参数（`child`）是任何[可渲染的 React 子元素](/docs/react-component.html#render)，例如一个元素，字符串或 fragment。第二个参数（`container`）是一个 DOM 元素。
 
-## Usage {#usage}
+## 用法 {#usage}
 
-Normally, when you return an element from a component's render method, it's mounted into the DOM as a child of the nearest parent node:
+通常来讲，当你从组件的 render 方法返回一个元素时，该元素将被挂载到 DOM 节点中离其最近的父节点：
 
 ```js{4,6}
 render() {
-  // React mounts a new div and renders the children into it
+  // React 挂载了一个新的 div，并且把子元素渲染其中
   return (
     <div>
       {this.props.children}
@@ -27,34 +27,34 @@ render() {
 }
 ```
 
-However, sometimes it's useful to insert a child into a different location in the DOM:
+然而，有时候将子元素插入到 DOM 节点中的不同位置也是有好处的：
 
 ```js{6}
 render() {
-  // React does *not* create a new div. It renders the children into `domNode`.
-  // `domNode` is any valid DOM node, regardless of its location in the DOM.
+  // React 并*没有*创建一个新的 div。它只是把子元素渲染到 `domNode` 中。
+  // `domNode` 是一个可以在任何位置的有效 DOM 节点。
   return ReactDOM.createPortal(
     this.props.children,
     domNode
   );
 }
 ```
 
-A typical use case for portals is when a parent component has an `overflow: hidden` or `z-index` style, but you need the child to visually "break out" of its container. For example, dialogs, hovercards, and tooltips.
+一个 portal 的典型用例是当父组件有 `overflow: hidden` 或 `z-index` 样式时，但你需要子组件能够在视觉上“跳出”其容器。例如，对话框、悬浮卡以及提示框：
 
-> Note:
+> 注意:
+> 
+> 当在使用 portal 时, 记住[管理键盘焦点](/docs/accessibility.html#programmatically-managing-focus)就变得尤为重要。
 >
-> When working with portals, remember that [managing keyboard focus](/docs/accessibility.html#programmatically-managing-focus) becomes very important.
->
-> For modal dialogs, ensure that everyone can interact with them by following the [WAI-ARIA Modal Authoring Practices](https://www.w3.org/TR/wai-aria-practices-1.1/#dialog_modal).
+> 对于模态对话框，通过遵循 [WAI-ARIA 模态开发实践](https://www.w3.org/TR/wai-aria-practices-1.1/#dialog_modal)，来确保每个人都能够运用它。
 
-[**Try it on CodePen**](https://codepen.io/gaearon/pen/yzMaBd)
+[**在 CodePen 上尝试**](https://codepen.io/gaearon/pen/yzMaBd)
 
-## Event Bubbling Through Portals {#event-bubbling-through-portals}
+## 通过 Portal 进行事件冒泡 {#event-bubbling-through-portals}
 
-Even though a portal can be anywhere in the DOM tree, it behaves like a normal React child in every other way. Features like context work exactly the same regardless of whether the child is a portal, as the portal still exists in the *React tree* regardless of position in the *DOM tree*.
+尽管 portal 可以被放置在 DOM 树中的任何地方，但在任何其他方面，其行为和普通的 React 子节点行为一致。由于 portal 仍存在于 *React 树*， 且与 *DOM 树* 中的位置无关，那么无论其子节点是否是 portal，像 context 这样的功能特性都是不变的。
 
-This includes event bubbling. An event fired from inside a portal will propagate to ancestors in the containing *React tree*, even if those elements are not ancestors in the *DOM tree*. Assuming the following HTML structure:
+这包含事件冒泡。一个从 portal 内部触发的事件会一直冒泡至包含 *React 树*的祖先，即便这些元素并不是 *DOM 树* 中的祖先。假设存在如下 HTML 结构：
 
 ```html
 <html>
@@ -65,10 +65,10 @@ This includes event bubbling. An event fired from inside a portal will propagate
 </html>
 ```
 
-A `Parent` component in `#app-root` would be able to catch an uncaught, bubbling event from the sibling node `#modal-root`.
+在 `#app-root` 里的 `Parent` 组件能够捕获到未被捕获的从兄弟节点 `#modal-root` 冒泡上来的事件。
 
 ```js{28-31,42-49,53,61-63,70-71,74}
-// These two containers are siblings in the DOM
+// 在 DOM 中有两个容器是兄弟级 （siblings）
 const appRoot = document.getElementById('app-root');
 const modalRoot = document.getElementById('modal-root');
 
@@ -79,14 +79,14 @@ class Modal extends React.Component {
   }
 
   componentDidMount() {
-    // The portal element is inserted in the DOM tree after
-    // the Modal's children are mounted, meaning that children
-    // will be mounted on a detached DOM node. If a child
-    // component requires to be attached to the DOM tree
-    // immediately when mounted, for example to measure a
-    // DOM node, or uses 'autoFocus' in a descendant, add
-    // state to Modal and only render the children when Modal
-    // is inserted in the DOM tree.
+    // 在 Modal 的所有子元素被挂载后，
+    // 这个 portal 元素会被嵌入到 DOM 树中，
+    // 这意味着子元素将被挂载到一个分离的 DOM 节点中。
+    // 如果要求子组件在挂载时可以立刻接入 DOM 树，
+    // 例如衡量一个 DOM 节点，
+    // 或者在后代节点中使用 ‘autoFocus’，
+    // 则需添加 state 到 Modal 中，
+    // 仅当 Modal 被插入 DOM 树中才能渲染子元素。
     modalRoot.appendChild(this.el);
   }
 
@@ -110,9 +110,9 @@ class Parent extends React.Component {
   }
 
   handleClick() {
-    // This will fire when the button in Child is clicked,
-    // updating Parent's state, even though button
-    // is not direct descendant in the DOM.
+    // 当子元素里的按钮被点击时，
+    // 这个将会被触发更新父元素的 state，
+    // 即使这个按钮在 DOM 中不是直接关联的后代
     this.setState(state => ({
       clicks: state.clicks + 1
     }));
@@ -137,8 +137,8 @@ class Parent extends React.Component {
 }
 
 function Child() {
-  // The click event on this button will bubble up to parent,
-  // because there is no 'onClick' attribute defined
+  // 这个按钮的点击事件会冒泡到父元素
+  // 因为这里没有定义 'onClick' 属性
   return (
     <div className="modal">
       <button>Click</button>
@@ -149,6 +149,6 @@ function Child() {
 ReactDOM.render(<Parent />, appRoot);
 ```
 
-[**Try it on CodePen**](https://codepen.io/gaearon/pen/jGBWpE)
+[**在 CodePen 上尝试**](https://codepen.io/gaearon/pen/jGBWpE)
 
-Catching an event bubbling up from a portal in a parent component allows the development of more flexible abstractions that are not inherently reliant on portals. For example, if you render a `<Modal />` component, the parent can capture its events regardless of whether it's implemented using portals.
+在父组件里捕获一个来自 portal 冒泡上来的事件，使之能够在开发时具有不完全依赖于 portal 的更为灵活的抽象。例如，如果你在渲染一个 `<Modal />` 组件，无论其是否采用 portal 实现，父组件都能够捕获其事件。
