[JS][7kyu] Back to the Future?

codewars/7kyu/back-to-the-future/koronya.js

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+// [JS][7kyu] Back to the Future?
+// back-to-the-future
+// https://www.codewars.com/kata/5964e8fcfc9cf7749000005e/train/javascript
+
+const monthMap = new Map([
+  ['January', 'October'],
+  ['April', 'July'],
+  ['September', 'December'],
+  ['February', 'March'],
+  ['March', 'November'],
+])
+
+const backToTheFuture = (str) => {
+  const [dayOfWeek, day, month] = str.split(' ')
+  if (!monthMap.has(month)) {
+    return "Doc, I can't get back to the future!"
+  }
+  const newMonth = monthMap.get(month)
+  if (newMonth === 'November' && day === '31') {
+    return "Doc, I can't get back to the future!"
+  }
+  return `I'm leaving here on ${dayOfWeek} ${day} ${newMonth}!`
+}
+
+// backToTheFuture('Monday 3 January') === "I'm leaving here on Monday 3 October!"
+// backToTheFuture('Friday 20 October') === "Doc, I can't get back to the future!"
+// backToTheFuture('Tuesday 31 March') === "Doc, I can't get back to the future!", 'Matching months do not necessarily have same number of days'
+// backToTheFuture('Saturday 26 July') === "Doc, I can't get back to the future!"