feat: add Absolute value algorithm

Maths/AbsoluteValue.js

@@ -0,0 +1,19 @@
+/**
+ * @function absoluteValue
+ * @description Returns the absolute value of a number without using
+ *   JavaScript's built-in Math.abs() function.
+ * @param {number} n - Any real number
+ * @returns {number} - The absolute value of n
+ * @see https://en.wikipedia.org/wiki/Absolute_value
+ * @example absoluteValue(-5) => 5
+ * @example absoluteValue(3) => 3
+ * @example absoluteValue(0) => 0
+ */
+const absoluteValue = (n) => {
+  if (typeof n !== 'number' || isNaN(n)) {
+    throw new TypeError('Input must be a number')
+  }
+  return n < 0 ? -n : n === 0 ? 0 : n
+}
+
+export { absoluteValue }

Maths/test/AbsoluteValue.test.js

@@ -0,0 +1,31 @@
+import { absoluteValue } from '../AbsoluteValue.js'
+
+describe('absoluteValue', () => {
+  test('absoluteValue(-5) returns 5', () => {
+    expect(absoluteValue(-5)).toBe(5)
+  })
+
+  test('absoluteValue(3) returns 3', () => {
+    expect(absoluteValue(3)).toBe(3)
+  })
+
+  test('absoluteValue(0) returns 0', () => {
+    expect(absoluteValue(0)).toBe(0)
+  })
+
+  test('absoluteValue(-99.99) returns 99.99', () => {
+    expect(absoluteValue(-99.99)).toBe(99.99)
+  })
+
+  test('absoluteValue(100) returns 100', () => {
+    expect(absoluteValue(100)).toBe(100)
+  })
+
+  test('throws TypeError for non-number input', () => {
+    expect(() => absoluteValue('abc')).toThrow(TypeError)
+  })
+
+  test('throws TypeError for NaN', () => {
+    expect(() => absoluteValue(NaN)).toThrow(TypeError)
+  })
+})