feat(Stepper): add decimalLength prop (#2087)

example/pages/stepper/index.wxml

@@ -18,6 +18,10 @@
   <van-stepper value="{{ 1 }}" disabled />
 </van-cell>
 
+<van-cell center title="固定小数位数">
+  <van-stepper value="{{ 1 }}" step="0.2" decimal-length="{{ 1 }}" />
+</van-cell>
+
 <van-cell center title="异步变更">
   <van-stepper
     value="{{ value }}"

packages/stepper/README.md

@@ -64,6 +64,14 @@ Page({
 <van-stepper value="{{ 1 }}" disabled />
 ```
 
+### 固定小数位数
+
+通过设置`decimal-length`属性可以保留固定的小数位数
+
+```html
+<van-stepper value="{{ 1 }}" step="0.2" decimal-length="{{ 1 }}" />
+```
+
 ### 异步变更
 
 如果需要异步地修改输入框的值，可以设置`async-change`属性，并在`change`事件中手动修改`value`
@@ -116,6 +124,7 @@ Page({
 | button-size | 按钮大小，默认单位为 `px`，输入框高度会和按钮大小保持一致 | *string \| number* | `28px` | - |
 | show-plus | 是否显示增加按钮 | *boolean* | `true` | - |
 | show-minus | 是否显示减少按钮 | *boolean* | `true` | - |
+| decimal-length | 固定显示的小数位数 | *number* | - | - |
 
 ### Events
 

packages/stepper/index.ts

@@ -1,6 +1,6 @@
 import { VantComponent } from '../common/component';
 import { Weapp } from 'definitions/weapp';
-import { addUnit } from '../common/utils';
+import { addUnit, isDef } from '../common/utils';
 
 const LONG_PRESS_START_TIME = 600;
 const LONG_PRESS_INTERVAL = 200;
@@ -18,6 +18,7 @@ VantComponent({
     buttonSize: null,
     asyncChange: Boolean,
     disableInput: Boolean,
+    decimalLength: Number,
     min: {
       type: null,
       value: 1
@@ -101,7 +102,17 @@ VantComponent({
     // limit value range
     range(value) {
       value = String(value).replace(/[^0-9.-]/g, '');
-      return Math.max(Math.min(this.data.max, value), this.data.min);
+
+      // format range
+      value = value === '' ? 0 : +value;
+      value = Math.max(Math.min(this.data.max, value), this.data.min);
+
+      // format decimal
+      if (isDef(this.data.decimalLength)) {
+        value = value.toFixed(this.data.decimalLength);
+      }
+
+      return value;
     },
 
     onInput(event: Weapp.Event) {
@@ -117,7 +128,13 @@ VantComponent({
       }
 
       const diff = type === 'minus' ? -this.data.step : +this.data.step;
-      const value = Math.round((+this.data.value + diff) * 100) / 100;
+
+      let value = +this.data.value + diff;
+
+      if (!isDef(this.data.decimalLength)) {
+        value = Math.round(value * 100) / 100;
+      }
+
       this.triggerInput(this.range(value));
       this.$emit(type);
     },