chore: Add localeData plugin

src/plugin/localeData/index.js

@@ -0,0 +1,16 @@
+export default (o, c) => { // locale needed later
+  const proto = c.prototype
+  const localeData = function () {
+    return {
+      months: instance => instance.format('MMMM'),
+      monthsShort: instance => instance.format('MMM'),
+      firstDayOfWeek: () => this.$locale().weekStart || 0,
+      weekdaysMin: instance => instance.format('dd'),
+      weekdaysShort: instance => instance.format('ddd')
+    }
+  }
+  proto.localeData = function () {
+    return localeData.bind(this)()
+  }
+}
+

test/plugin/localeData.test.js

@@ -0,0 +1,26 @@
+import MockDate from 'mockdate'
+import moment from 'moment'
+import dayjs from '../../src'
+import localeData from '../../src/plugin/localeData'
+
+dayjs.extend(localeData)
+
+beforeEach(() => {
+  MockDate.set(new Date())
+})
+
+afterEach(() => {
+  MockDate.reset()
+})
+
+it('localeData', () => {
+  const d = dayjs()
+  const m = moment()
+  const dayjsLocaleData = dayjs().localeData()
+  const momentLocaleData = moment().localeData()
+  expect(dayjsLocaleData.firstDayOfWeek()).toBe(momentLocaleData.firstDayOfWeek())
+  expect(dayjsLocaleData.months(d)).toBe(momentLocaleData.months(m))
+  expect(dayjsLocaleData.monthsShort(d)).toBe(momentLocaleData.monthsShort(m))
+  expect(dayjsLocaleData.weekdaysMin(d)).toBe(momentLocaleData.weekdaysMin(m))
+  expect(dayjsLocaleData.weekdaysShort(d)).toBe(momentLocaleData.weekdaysShort(m))
+})

types/plugin/localeData.d.ts

@@ -0,0 +1,10 @@
+import { PluginFunc } from 'dayjs'
+
+declare const plugin: PluginFunc
+export = plugin
+
+declare module 'dayjs' {
+  interface Dayjs {
+    localeData(): any
+  }
+}