chore(Calendar): code review

src/calendar/components/Header.js

@@ -0,0 +1,51 @@
+import { createNamespace } from '../../utils';
+import { t, bem, formatMonthTitle } from '../utils';
+
+const [createComponent] = createNamespace('calendar-header');
+
+export default createComponent({
+  props: {
+    title: String,
+    currentMonth: Date
+  },
+
+  methods: {
+    genTitle() {
+      const title = this.slots('title') || this.title || t('title');
+
+      if (title) {
+        return <div class={bem('header-title')}>{title}</div>;
+      }
+    },
+
+    genMonth() {
+      return (
+        <div class={bem('month-title')}>
+          {formatMonthTitle(this.currentMonth)}
+        </div>
+      );
+    },
+
+    genWeekDays() {
+      const weekdays = t('weekdays');
+
+      return (
+        <div class={bem('weekdays')}>
+          {weekdays.map(item => (
+            <span class={bem('weekday')}>{item}</span>
+          ))}
+        </div>
+      );
+    }
+  },
+
+  render() {
+    return (
+      <div class={bem('header')}>
+        {this.genTitle()}
+        {this.genMonth()}
+        {this.genWeekDays()}
+      </div>
+    );
+  }
+});