Add Get Numbers of Days of a Month (#464)

Timing-Functions/GetMonthDays.js

@@ -0,0 +1,33 @@
+/**
+  function that takes month number and its year and returns the number of days within it
+  * @param monthNumber.
+  * @param year.
+  e.g.: mahfoudh.arous@gmail.com -> true
+  e.g.: mahfoudh.arous.com ->false
+*/
+
+const getMonthDays = (monthNumber, year) => {
+  const the31DaysMonths = [1, 3, 5, 7, 8, 10, 12]
+  const the30DaysMonths = [4, 6, 9, 11]
+
+  if (!the31DaysMonths.includes(monthNumber) && !the30DaysMonths.includes(monthNumber) &&
+    (monthNumber !== 2)
+  ) {
+    throw new TypeError('Invalid Month Number.')
+  }
+
+  if (the31DaysMonths.includes(monthNumber)) { return 31 }
+
+  if (the30DaysMonths.includes(monthNumber)) { return 30 }
+
+  // Check for Leap year
+  if (year % 4 === 0) {
+    if ((year % 100 !== 0) || (year % 100 === 0 && year % 400 === 0)) {
+      return 29
+    }
+  }
+
+  return 28
+}
+
+export { getMonthDays }

Timing-Functions/GetMonthDays.test.js

@@ -0,0 +1,19 @@
+import { getMonthDays } from './GetMonthDays'
+
+describe('Get the Days of a Month', () => {
+  it('expects to return 28', () => {
+    expect(getMonthDays(2, 2018)).toEqual(28)
+  })
+
+  it('expects to return 30', () => {
+    expect(getMonthDays(6, 254)).toEqual(30)
+  })
+
+  it('expects to return 29', () => {
+    expect(getMonthDays(2, 2024)).toEqual(29)
+  })
+
+  it('expects to throw a type error', () => {
+    expect(() => { getMonthDays(13, 2020) }).toThrow('Invalid Month Number.')
+  })
+})