Feat: IsEven and IsOdd

Author: patrickwestervelt

Maths/IsEven.ts

@@ -0,0 +1,16 @@
+/**
+ * @function IsEven
+ * @description Determine whether a number is even.
+ * @param {Number} num - A number.
+ * @return {Boolean} - Whether the given number is even.
+ * @see https://en.wikipedia.org/wiki/Parity_(mathematics)
+ * @example IsEven(1) = false
+ * @example IsEven(2) = true
+ */
+ export const IsEven = (num: number): boolean => {
+    if (!Number.isInteger(num)) {
+      throw new Error("only integers can be even or odd");
+    }
+  
+    return num % 2 === 0;
+  };

Maths/IsOdd.ts

@@ -0,0 +1,16 @@
+/**
+ * @function IsOdd
+ * @description Determine whether a number is odd.
+ * @param {Number} num - A number.
+ * @return {Boolean} - Whether the given number is odd.
+ * @see https://en.wikipedia.org/wiki/Parity_(mathematics)
+ * @example IsOdd(1) = true
+ * @example IsOdd(2) = false
+ */
+ export const IsOdd = (num: number): boolean => {
+    if (!Number.isInteger(num)) {
+      throw new Error("only integers can be even or odd");
+    }
+  
+    return num % 2 !== 0;
+  };

Maths/test/IsEven.test.ts

@@ -0,0 +1,16 @@
+import { IsEven } from "../IsEven";
+
+describe("IsEven", () => {
+  test.each([[2, true], [1, false], [0, true], [-1, false], [-2, true]])(
+    "correct output for for %i",
+    (nums, expected) => {
+      expect(IsEven(nums)).toBe(expected);
+    },
+  );
+
+  test("only whole numbers should be accepted", () => {
+    expect(() => IsEven(0.5)).toThrowError(
+      "only integers can be even or odd",
+    );
+  });
+});

Maths/test/IsOdd.test.ts

@@ -0,0 +1,16 @@
+import { IsOdd } from "../IsOdd";
+
+describe("IsOdd", () => {
+  test.each([[2, false], [1, true], [0, false], [-1, true], [-2, false]])(
+    "correct output for for %i",
+    (nums, expected) => {
+      expect(IsOdd(nums)).toBe(expected);
+    },
+  );
+
+  test("only whole numbers should be accepted", () => {
+    expect(() => IsOdd(0.5)).toThrowError(
+      "only integers can be even or odd",
+    );
+  });
+});