refactor(date picker): refactor setExcludedDates for readability and …

…to appease eslint

The large map function in the setExcldedDates method was hard to read, and eslint didn't like it
didn't have an obvious return value. This commit refactors part of the
map into a parseDateRangeString function making the code much more
readable and control flow more obvious.

src/moj/components/date-picker/date-picker.js

@@ -361,29 +361,38 @@ Datepicker.prototype.setExcludedDates = function () {
       .replace(/\s+/, " ")
       .split(" ")
       .map((item) => {
-        if (item.includes("-")) {
-          // parse the date range from the format "dd/mm/yyyy-dd/mm/yyyy"
-          const [startDate, endDate] = item
-            .split("-")
-            .map((d) => this.formattedDateFromString(d, null));
-          if (startDate && endDate) {
-            const date = new Date(startDate.getTime());
-            const dates = [];
-            while (date <= endDate) {
-              dates.push(new Date(date));
-              date.setDate(date.getDate() + 1);
-            }
-            return dates;
-          }
-        } else {
-          return this.formattedDateFromString(item, null);
-        }
+        return item.includes("-")
+          ? this.parseDateRangeString(item)
+          : this.formattedDateFromString(item);
       })
       .flat()
       .filter((item) => item);
   }
 };
 
+/*
+ * Parses a daterange string into an array of dates
+ * @param {String} datestring - A daterange string in the format "dd/mm/yyyy-dd/mm/yyyy"
+ * @returns {Date[]}
+ */
+Datepicker.prototype.parseDateRangeString = function (datestring) {
+  const dates = [];
+  const [startDate, endDate] = datestring
+    .split("-")
+    .map((d) => this.formattedDateFromString(d, null));
+
+  if (startDate && endDate) {
+    const date = new Date(startDate.getTime());
+    /* eslint-disable no-unmodified-loop-condition */
+    while (date <= endDate) {
+      dates.push(new Date(date));
+      date.setDate(date.getDate() + 1);
+    }
+    /* eslint-enable no-unmodified-loop-condition */
+  }
+  return dates;
+};
+
 Datepicker.prototype.setExcludedDays = function () {
   if (this.config.excludedDays) {
     // lowercase and arrange dayLabels to put indexOf sunday == 0 for comparison
@@ -788,7 +797,7 @@ Datepicker.prototype.focusPreviousYear = function (event, focus = true) {
 Datepicker.prototype.parseDataset = function (schema, dataset) {
   const parsed = {};
 
-  for (const [field, attributes] of Object.entries(schema.properties)) {
+  for (const [field, ,] of Object.entries(schema.properties)) {
     if (field in dataset) {
       parsed[field] = dataset[field];
     }
@@ -860,12 +869,12 @@ DSCalendarDay.prototype.init = function () {
  * @param {boolean} disabled - is the day selectable or excluded
  */
 DSCalendarDay.prototype.update = function (day, hidden, disabled) {
-  let label = day.getDate();
+  const label = day.getDate();
   let accessibleLabel = this.picker.formattedDateHuman(day);
 
   if (disabled) {
     this.button.setAttribute("aria-disabled", true);
-    accessibleLabel = "Excluded date, " + accessibleLabel;
+    accessibleLabel = `Excluded date, ${accessibleLabel}`;
   } else {
     this.button.removeAttribute("aria-disabled");
   }