feat(maths): added Factors

maths/factors.ts

@@ -0,0 +1,34 @@
+/**
+ * @function FindFactors
+ * @description Find all the factors of a natural number.
+ * @param {number} num - A natural number.
+ * @return {number[]} - An array of all the factors of given natural number.
+ * @see https://en.wikipedia.org/wiki/Divisor
+ * @example FindFactors(1) = [1]
+ * @example FindFactors(4) = [1,2,4]
+ * @example FindFactors(16) = [1,3,5,15]
+ */
+
+export const FindFactors = (num: number): number[] => {
+  if (num <= 0 || !Number.isInteger(num)) {
+    throw new Error("only natural numbers are supported");
+  }
+
+  const res: number[] = [];
+  // iterate from 1 to square root of num
+  // push factors into the res array
+  let i: number = 1;
+  while (i * i <= num) {
+    if (num % i === 0) {
+      res.push(i);
+      // if i is the same as num / i
+      const sqrtFactor = Math.floor(num / i);
+      if (sqrtFactor !== i) {
+        res.push(sqrtFactor);
+      }
+    }
+    i++;
+  }
+
+  return res;
+};

maths/test/factors.test.ts

@@ -0,0 +1,19 @@
+import { FindFactors } from "../factors";
+
+describe("FindFactors", () => {
+  test.each([-890, -5.56, -7, 0, 0.73, 4.2, NaN, -Infinity, Infinity])(
+    "should throw an error for non natural number %d",
+    (num) => {
+      expect(() => FindFactors(num)).toThrowError(
+        "only natural numbers are supported",
+      );
+    },
+  );
+
+  test.each([[1, [1]], [2, [1,2]], [4, [1,4,2]], [6, [1,6,2,3]], [16, [1,16,2,8,4]]])(
+    "of %i should return the correct array of its factors",
+    (num, expected) => {
+      expect(FindFactors(num)).toStrictEqual(expected);
+    },
+  );
+});