refactor: change 'var' to 'let' and 'const'

src/calendar.jsx

@@ -861,18 +861,18 @@ export default class Calendar extends React.Component {
       return;
     }
 
-    var monthList = [];
-    var monthsToSubtract = this.props.showPreviousMonths
+    const monthList = [];
+    const monthsToSubtract = this.props.showPreviousMonths
       ? this.props.monthsShown - 1
       : 0;
-    var fromMonthDate = subMonths(this.state.date, monthsToSubtract);
-    var monthSelectedIn = this.props.monthSelectedIn ?? monthsToSubtract;
-    for (var i = 0; i < this.props.monthsShown; ++i) {
-      var monthsToAdd = i - monthSelectedIn + monthsToSubtract;
-      var monthDate = addMonths(fromMonthDate, monthsToAdd);
-      var monthKey = `month-${i}`;
-      var monthShowsDuplicateDaysEnd = i < this.props.monthsShown - 1;
-      var monthShowsDuplicateDaysStart = i > 0;
+    const fromMonthDate = subMonths(this.state.date, monthsToSubtract);
+    const monthSelectedIn = this.props.monthSelectedIn ?? monthsToSubtract;
+    for (let i = 0; i < this.props.monthsShown; ++i) {
+      const monthsToAdd = i - monthSelectedIn + monthsToSubtract;
+      const monthDate = addMonths(fromMonthDate, monthsToAdd);
+      const monthKey = `month-${i}`;
+      const monthShowsDuplicateDaysEnd = i < this.props.monthsShown - 1;
+      const monthShowsDuplicateDaysStart = i > 0;
       monthList.push(
         <div
           key={monthKey}

src/date_utils.js

@@ -60,7 +60,7 @@ export const DEFAULT_YEAR_ITEM_NUMBER = 12;
 
 // This RegExp catches symbols escaped by quotes, and also
 // sequences of symbols P, p, and the combinations like `PPPPPPPppppp`
-var longFormattingTokensRegExp = /P+p+|P+|p+|''|'(''|[^'])+('|$)|./g;
+const longFormattingTokensRegExp = /P+p+|P+|p+|''|'(''|[^'])+('|$)|./g;
 
 // ** Date Constructors **
 
@@ -105,9 +105,9 @@ export function parseDate(value, dateFormat, locale, strictParsing, minDate) {
     dateFormat = dateFormat
       .match(longFormattingTokensRegExp)
       .map(function (substring) {
-        var firstCharacter = substring[0];
+        const firstCharacter = substring[0];
         if (firstCharacter === "p" || firstCharacter === "P") {
-          var longFormatter = longFormatters[firstCharacter];
+          const longFormatter = longFormatters[firstCharacter];
           return localeObject
             ? longFormatter(substring, localeObject.formatLong)
             : firstCharacter;
@@ -497,8 +497,8 @@ export function isQuarterDisabled(
 
 /**
  * @param {number} year
- * @param {date} start
- * @param {date} end
+ * @param {Date} start
+ * @param {Date} end
  * @returns {boolean}
  */
 export function isYearInRange(year, start, end) {

src/month.jsx

@@ -74,7 +74,7 @@ export default class Month extends React.Component {
     fixedHeight: PropTypes.bool,
     formatWeekNumber: PropTypes.func,
     highlightDates: PropTypes.instanceOf(Map),
-    holidays: PropTypes.PropTypes.instanceOf(Map),
+    holidays: PropTypes.instanceOf(Map),
     includeDates: PropTypes.array,
     includeDateIntervals: PropTypes.array,
     inline: PropTypes.bool,
@@ -592,7 +592,7 @@ export default class Month extends React.Component {
       minDate,
       maxDate,
       preSelection,
-      disabledKeyboardNavigation
+      disabledKeyboardNavigation,
     } = this.props;
     return classnames(
       "react-datepicker__quarter-text",

src/year_dropdown.jsx

@@ -4,7 +4,7 @@ import YearDropdownOptions from "./year_dropdown_options";
 import onClickOutside from "react-onclickoutside";
 import { getYear } from "./date_utils";
 
-var WrappedYearDropdownOptions = onClickOutside(YearDropdownOptions);
+const WrappedYearDropdownOptions = onClickOutside(YearDropdownOptions);
 
 export default class YearDropdown extends React.Component {
   static propTypes = {

src/year_dropdown_options.jsx

@@ -4,8 +4,8 @@ import classNames from "classnames";
 import { getYear } from "./date_utils";
 
 function generateYears(year, noOfYear, minDate, maxDate) {
-  var list = [];
-  for (var i = 0; i < 2 * noOfYear + 1; i++) {
+  const list = [];
+  for (let i = 0; i < 2 * noOfYear + 1; i++) {
     const newYear = year + noOfYear - i;
     let isInRange = true;
 
@@ -73,8 +73,8 @@ export default class YearDropdownOptions extends React.Component {
   }
 
   renderOptions = () => {
-    var selectedYear = this.props.year;
-    var options = this.state.yearsList.map((year) => (
+    const selectedYear = this.props.year;
+    const options = this.state.yearsList.map((year) => (
       <div
         className={
           selectedYear === year
@@ -133,7 +133,7 @@ export default class YearDropdownOptions extends React.Component {
   };
 
   shiftYears = (amount) => {
-    var years = this.state.yearsList.map(function (year) {
+    const years = this.state.yearsList.map(function (year) {
       return year + amount;
     });