Fix default argument value usage (#2423)

Fixed a breaking change introduced by using modern default argument value syntax (see Hacker0x01/react-datepicker#2870).

src/formatDuration/index.js

@@ -7,7 +7,7 @@ const defaultFormat = [
   'days',
   'hours',
   'minutes',
-  'seconds'
+  'seconds',
 ]
 
 /**
@@ -73,21 +73,21 @@ const defaultFormat = [
  * formatDuration({ years: 2, months: 9, weeks: 3 }, { delimiter: ', ' })
  * //=> '2 years, 9 months, 3 weeks'
  */
-export default function formatDuration(duration, options = {}) {
+export default function formatDuration(duration, options) {
   if (arguments.length < 1) {
     throw new TypeError(
       `1 argument required, but only ${arguments.length} present`
     )
   }
 
-  const format = options.format || defaultFormat
-  const locale = options.locale || defaultLocale
-  const zero = options.zero || false
-  const delimiter = options.delimiter || ' '
+  const format = options?.format || defaultFormat
+  const locale = options?.locale || defaultLocale
+  const zero = options?.zero || false
+  const delimiter = options?.delimiter || ' '
 
   const result = format
     .reduce((acc, unit) => {
-      const token = `x${unit.replace(/(^.)/, m => m.toUpperCase())}`
+      const token = `x${unit.replace(/(^.)/, (m) => m.toUpperCase())}`
       const addChunk =
         typeof duration[unit] === 'number' && (zero || duration[unit])
       return addChunk

src/getWeekYear/index.ts

@@ -53,22 +53,21 @@ import {
  */
 export default function getWeekYear(
   dirtyDate: Date | number,
-  options: LocaleOptions & WeekStartOptions & FirstWeekContainsDateOptions = {}
+  options?: LocaleOptions & WeekStartOptions & FirstWeekContainsDateOptions
 ): number {
   requiredArgs(1, arguments)
 
   const date = toDate(dirtyDate)
   const year = date.getFullYear()
 
-  const locale = options.locale
   const localeFirstWeekContainsDate =
-    locale && locale.options && locale.options.firstWeekContainsDate
+    options?.locale?.options?.firstWeekContainsDate
   const defaultFirstWeekContainsDate =
     localeFirstWeekContainsDate == null
       ? 1
       : toInteger(localeFirstWeekContainsDate)
   const firstWeekContainsDate =
-    options.firstWeekContainsDate == null
+    options?.firstWeekContainsDate == null
       ? defaultFirstWeekContainsDate
       : toInteger(options.firstWeekContainsDate)
 

src/getWeeksInMonth/index.ts

@@ -35,7 +35,10 @@ import { LocaleOptions, WeekStartOptions } from '../types'
  * const result = getWeeksInMonth(new Date(2017, 6, 5), { weekStartsOn: 1 })
  * //=> 6
  */
-export default function getWeeksInMonth(date: Date | number, options: LocaleOptions & WeekStartOptions = {}): number {
+export default function getWeeksInMonth(
+  date: Date | number,
+  options?: LocaleOptions & WeekStartOptions
+): number {
   requiredArgs(1, arguments)
 
   return (