Merge pull request alibaba#1458 from alibaba/doc-feature-textarea

*[doc] textarea

Author: Jinjiang

doc/SUMMARY.md

@@ -49,6 +49,7 @@
         * [text](/components/text.md)
         * [image](/components/image.md)
         * [input](/components/input.md)
+        * [textarea](/components/textarea.md)
         * [switch](/components/switch.md)
         * [slider](/components/slider.md)
             * [indicator](/components/indicator.md)

doc/components/textarea.md

@@ -0,0 +1,75 @@
+# <textarea>
+<span class="weex-version">0.8</span>
+<a href="https://github.com/weexteam/article/issues/95"  class="weex-translate">cn</a>
+
+
+### Summary
+
+The weex builtin component ``textarea`` is used to create interactive controls to accept data from users. It can be a multi-line [input](./input.md).
+
+**Notes:** `<textarea>` support all event which `<input>` had.
+
+### Child Components
+
+This component supports no child components.
+
+### attributes
+
+- `value`: &lt;string&gt; the value of the control.
+- `placeholder`: &lt;string&gt; a hint to the user of which can be entered to the control. The placeholder text must have no carriage returns or line-feeds.
+- `disabled`: &lt;boolean&gt; a boolean attribute indicates that the form control is not available for interaction. In particular, the click event will not be dispatched on disabled controls.
+- `autofocus`: &lt;boolean&gt; a boolean attribute lets you specify that a form control should have input focus when the page loads.
+- `rows:`&lt;number&gt; a number which can specify the height of textarea, default is `2`.
+
+Other attributes please check out the [common attributes](../references/common-attrs.md).
+
+### Styles
+
+**text styles**: checkout [text styles](../references/text-style.md)
+
+- support `color` style.
+- support `font-size` style.
+- support `font-style` style.
+- support `font-weight` style.
+- support `text-align` style.
+
+
+**common styles**: check out [common styles for components](../references/common-style.md)
+
+- support flexbox related styles.
+- support box model related styles.
+- support ``position`` related styles.
+- support ``opacity``, ``background-color`` etc.
+
+### Events
+
+- `input`: the value of an element changes.
+- `change`: the change event is fired when a change to the component's value is commited by the user. It always come after a ``blur`` event.
+- `focus`: a component has received focus.
+- `blur`: a component has lost focus.
+
+**common events**: check out the [common events](../references/common-event.md)
+
+- support `appear` / `disappear` event. Check out [common events](../references/common-event.md).
+
+**Notes:** `<textarea>` does not support the common-event `click`. Please listen to the `input` or `change` event instead.
+
+### Parameters of events' object
+
+- for ``input`` and ``change`` events:
+  - `value`: the value of the component who dispatched this event.
+  - `timestamp`: the time stamp of the event.
+- for ``focus`` and ``blur`` events:
+  - `timestamp`: the time stamp of the event.
+
+### Example
+
+```
+<div>
+  <textarea
+    autofocus="true"
+    placeholder="..."
+    value="I am a multiple input">
+  </textarea>
+</div>
+```