From 6c71a452445e9db4729582f66c10ecccafe88866 Mon Sep 17 00:00:00 2001
From: sarthakgupta1907-cell <sarthakgupta1907@gmail.com>
Date: Mon, 2 Nov 2026 18:25:41 +0530
Subject: [PATCH] feat: add decimal to binary conversion

---
 Conversions/DecimalToBinary.js           | 36 +++++++++-------
 Conversions/test/DecimalToBinary.test.js | 53 +++++++++++++++---------
 2 files changed, 55 insertions(+), 34 deletions(-)

diff --git a/Conversions/DecimalToBinary.js b/Conversions/DecimalToBinary.js
index 03b0df8bea..c2addf8d75 100644
--- a/Conversions/DecimalToBinary.js
+++ b/Conversions/DecimalToBinary.js
@@ -1,19 +1,27 @@
-function decimalToBinary(num) {
-  const bin = []
+/**
+ * @function decimalToBinary
+ * @description Converts a decimal number (base-10) to its binary
+ *   (base-2) string representation without using JavaScript's
+ *   built-in toString(2).
+ * @param {number} decimal - A non-negative integer
+ * @returns {string} - The binary string representation of the decimal number
+ * @see https://en.wikipedia.org/wiki/Binary_number
+ * @example decimalToBinary(10) => "1010"
+ * @example decimalToBinary(255) => "11111111"
+ * @example decimalToBinary(0) => "0"
+ */
+const decimalToBinary = (decimal) => {
+  if (!Number.isInteger(decimal) || decimal < 0) {
+    throw new TypeError('Input must be a non-negative integer')
+  }
+  if (decimal === 0) return '0'
+  let binary = ''
+  let num = decimal
   while (num > 0) {
-    bin.unshift(num % 2)
-    num >>= 1 // basically /= 2 without remainder if any
+    binary = (num % 2).toString() + binary
+    num = Math.floor(num / 2)
   }
-  return bin.join('')
+  return binary
 }
 
 export { decimalToBinary }
-
-// > decimalToBinary(2)
-// '10'
-
-// > decimalToBinary(7)
-// '111'
-
-// > decimalToBinary(35)
-// '100011'
diff --git a/Conversions/test/DecimalToBinary.test.js b/Conversions/test/DecimalToBinary.test.js
index b3a26e1b76..29c05d51ca 100644
--- a/Conversions/test/DecimalToBinary.test.js
+++ b/Conversions/test/DecimalToBinary.test.js
@@ -1,26 +1,39 @@
-import { decimalToBinary } from '../DecimalToBinary'
+import { decimalToBinary } from '../DecimalToBinary.js'
 
-test('The Binary representation of 35 is 100011', () => {
-  const res = decimalToBinary(35)
-  expect(res).toBe('100011')
-})
+describe('decimalToBinary', () => {
+  test("decimalToBinary(0) returns '0'", () => {
+    expect(decimalToBinary(0)).toBe('0')
+  })
 
-test('The Binary representation of 1 is 1', () => {
-  const res = decimalToBinary(1)
-  expect(res).toBe('1')
-})
+  test("decimalToBinary(1) returns '1'", () => {
+    expect(decimalToBinary(1)).toBe('1')
+  })
 
-test('The Binary representation of 1000 is 1111101000', () => {
-  const res = decimalToBinary(1000)
-  expect(res).toBe('1111101000')
-})
+  test("decimalToBinary(10) returns '1010'", () => {
+    expect(decimalToBinary(10)).toBe('1010')
+  })
 
-test('The Binary representation of 2 is 10', () => {
-  const res = decimalToBinary(2)
-  expect(res).toBe('10')
-})
+  test("decimalToBinary(15) returns '1111'", () => {
+    expect(decimalToBinary(15)).toBe('1111')
+  })
+
+  test("decimalToBinary(32) returns '100000'", () => {
+    expect(decimalToBinary(32)).toBe('100000')
+  })
+
+  test("decimalToBinary(255) returns '11111111'", () => {
+    expect(decimalToBinary(255)).toBe('11111111')
+  })
+
+  test('throws TypeError for negative input', () => {
+    expect(() => decimalToBinary(-1)).toThrow(TypeError)
+  })
+
+  test('throws TypeError for float input', () => {
+    expect(() => decimalToBinary(1.5)).toThrow(TypeError)
+  })
 
-test('The Binary representation of 17 is 10001', () => {
-  const res = decimalToBinary(17)
-  expect(res).toBe('10001')
+  test('throws TypeError for non-number input', () => {
+    expect(() => decimalToBinary('10')).toThrow(TypeError)
+  })
 })