[improvement] Tab: optimize transition (#2151)

packages/tab/en-US.md

@@ -153,7 +153,7 @@ In swipeable mode, you can switch tabs with swipe gestrue in the content
 | v-model | Index of active tab | `String` `Number` | `0` |
 | color | Tab color | `String` | `#f44` |
 | type | Can be set to `line` `card` | `String` | `line` |
-| duration | Toggle tab's animation time | `Number` | `0.4` | - |
+| duration | Toggle tab's animation time | `Number` | `0.3` | - |
 | line-width | Width of tab line (px) | `Number` | Width of active tab |
 | swipe-threshold | Set swipe tabs threshold | `Number` | `4` | - |
 | sticky | Whether to use sticky mode | `Boolean` | `false` |

packages/tab/index.vue

@@ -1,7 +1,7 @@
 <template>
   <div
-    :class="b('pane', { float: parent.animated })"
     v-show="parent.animated || isSelected"
+    :class="b('pane', { float: parent.animated })"
     :style="paneStyle"
   >
     <slot v-if="inited" />

packages/tab/test/__snapshots__/demo.spec.js.snap

@@ -219,7 +219,7 @@ exports[`renders demo correctly 1`] = `
         </div>
       </div>
       <div class="van-tabs__content">
-        <div class="van-tabs__track" style="width:0px;transition-duration:0.4s;transform:translateX(0px);display:none;">
+        <div class="van-tabs__track" style="width:0px;transition-duration:0.3s;transform:translateX(0px);display:none;">
           <div class="van-tab__pane van-tab__pane--float">
             <!---->
             <!---->

packages/tab/zh-CN.md

@@ -157,7 +157,7 @@ export default {
 | v-model | 当前标签的索引 | `String` `Number` | `0` | 1.0.6 |
 | color | 标签颜色 | `String` | `#f44` | 1.2.0 |
 | type | 样式类型，可选值为`card` | `String` | `line` | - |
-| duration | 动画时间，单位秒 | `Number` | `0.4` | - |
+| duration | 动画时间，单位秒 | `Number` | `0.3` | - |
 | line-width | 底部条宽度，单位 px | `Number` | - | 1.1.1 |
 | swipeable | 是否开启手势滑动切换 | `Boolean` | `false` | 1.0.0 |
 | sticky | 是否使用粘性定位布局 | `Boolean` | `false` | - |