feat: add decimal to octal conversion

Conversions/DecimalToOctal.js

@@ -1,27 +1,27 @@
-function decimalToOctal(num) {
-  let oct = 0
-  let c = 0
+/**
+ * @function decimalToOctal
+ * @description Converts a decimal number (base-10) to its octal
+ *   (base-8) string representation without using JavaScript's
+ *   built-in toString(8).
+ * @param {number} decimal - A non-negative integer
+ * @returns {string} - The octal string representation of the decimal number
+ * @see https://en.wikipedia.org/wiki/Octal
+ * @example decimalToOctal(8) => "10"
+ * @example decimalToOctal(255) => "377"
+ * @example decimalToOctal(0) => "0"
+ */
+const decimalToOctal = (decimal) => {
+  if (!Number.isInteger(decimal) || decimal < 0) {
+    throw new TypeError('Input must be a non-negative integer')
+  }
+  if (decimal === 0) return '0'
+  let octal = ''
+  let num = decimal
   while (num > 0) {
-    const r = num % 8
-    oct = oct + r * Math.pow(10, c++)
-    num = Math.floor(num / 8) // basically /= 8 without remainder if any
+    octal = (num % 8).toString() + octal
+    num = Math.floor(num / 8)
   }
-  return oct
+  return octal
 }
 
 export { decimalToOctal }
-
-// > decimalToOctal(2)
-// 2
-
-// > decimalToOctal(8)
-// 10
-
-// > decimalToOctal(65)
-// 101
-
-// > decimalToOctal(216)
-// 330
-
-// > decimalToOctal(512)
-// 1000

Conversions/test/DecimalToOctal.test.js

@@ -1,26 +1,43 @@
-import { decimalToOctal } from '../DecimalToOctal'
+import { decimalToOctal } from '../DecimalToOctal.js'
 
-test('The Octal representation of 8 is 10', () => {
-  const res = decimalToOctal(8)
-  expect(res).toBe(10)
-})
+describe('decimalToOctal', () => {
+  test("decimalToOctal(0) returns '0'", () => {
+    expect(decimalToOctal(0)).toBe('0')
+  })
 
-test('The Octal representation of 1 is 1', () => {
-  const res = decimalToOctal(1)
-  expect(res).toBe(1)
-})
+  test("decimalToOctal(1) returns '1'", () => {
+    expect(decimalToOctal(1)).toBe('1')
+  })
 
-test('The Octal representation of 0 is 0', () => {
-  const res = decimalToOctal(0)
-  expect(res).toBe(0)
-})
+  test("decimalToOctal(7) returns '7'", () => {
+    expect(decimalToOctal(7)).toBe('7')
+  })
 
-test('The Octal representation of 100 is 144', () => {
-  const res = decimalToOctal(100)
-  expect(res).toBe(144)
-})
+  test("decimalToOctal(8) returns '10'", () => {
+    expect(decimalToOctal(8)).toBe('10')
+  })
+
+  test("decimalToOctal(64) returns '100'", () => {
+    expect(decimalToOctal(64)).toBe('100')
+  })
+
+  test("decimalToOctal(255) returns '377'", () => {
+    expect(decimalToOctal(255)).toBe('377')
+  })
+
+  test("decimalToOctal(512) returns '1000'", () => {
+    expect(decimalToOctal(512)).toBe('1000')
+  })
+
+  test('throws TypeError for negative input', () => {
+    expect(() => decimalToOctal(-1)).toThrow(TypeError)
+  })
+
+  test('throws TypeError for float input', () => {
+    expect(() => decimalToOctal(1.5)).toThrow(TypeError)
+  })
 
-test('The Octal representation of 111 is 157', () => {
-  const res = decimalToOctal(111)
-  expect(res).toBe(157)
+  test('throws TypeError for non-number input', () => {
+    expect(() => decimalToOctal('8')).toThrow(TypeError)
+  })
 })