Fix missing axis label formatter example
diff --git a/en/option/component/axis-common.md b/en/option/component/axis-common.md
index f059399..b897832 100644
--- a/en/option/component/axis-common.md
+++ b/en/option/component/axis-common.md
@@ -734,8 +734,14 @@
 ```js
 // Use string template; template variable is the default label of axis {value}
 formatter: '{value} kg'
+// Use callback.
+formatter: function (value, index) {
+    return value + 'kg';
+}
 ```
 
+---
+
 For axes of time [type](~${componentType}.type): `'time'`, `formatter` supports the following forms:
 
 - **String Templates**: an easy and fast way to make frequently used date/time template, formed in `string`
diff --git a/zh/option/component/axis-common.md b/zh/option/component/axis-common.md
index 4b9eaa4..580d0a7 100644
--- a/zh/option/component/axis-common.md
+++ b/zh/option/component/axis-common.md
@@ -729,8 +729,14 @@
 ```js
 // 使用字符串模板,模板变量为刻度默认标签 {value}
 formatter: '{value} kg'
+// 使用函数模板,函数参数分别为刻度数值(类目),刻度的索引
+formatter: function (value, index) {
+    return value + 'kg';
+}
 ```
 
+---
+
 对于时间轴([type](~${componentType}.type): `'time'`),`formatter` 的字符串模板支持多种形式:
 
 - **字符串模板**:简单快速实现常用日期时间模板,`string` 类型