--update: reverse a number

Author: ashokdey

README.md

@@ -1,4 +1,4 @@
-# Problem Solving Javascript
+# Problem Solving using Javascript
 
 [![Build Status](https://travis-ci.org/knaxus/problem-solving-javascript.svg?branch=master)](https://travis-ci.org/knaxus/problem-solving-javascript)
 [![Coverage Status](https://coveralls.io/repos/github/knaxus/problem-solving-javascript/badge.svg?branch=master)](https://coveralls.io/github/knaxus/problem-solving-javascript?branch=master)

src/reverse-number/index.js

@@ -0,0 +1,20 @@
+function reverseNumber(num) {
+  if (typeof num !== 'number') {
+    throw new Error('Invalid Argument');
+  }
+
+  let absNum = Math.abs(num);
+  let reverse = 0;
+
+  while (absNum > 0) {
+    const rem = absNum % 10;
+    reverse = reverse * 10 + rem;
+    absNum = parseInt(absNum / 10, 10); // important to get whole number
+  }
+
+  return reverse * Math.sign(num);
+}
+
+module.exports = {
+  reverseNumber,
+};

src/reverse-number/reverse-number.test.js

@@ -0,0 +1,23 @@
+const { reverseNumber } = require('.');
+
+describe('Reverse Numbers', () => {
+  it('Should return a number', () => {
+    expect(typeof reverseNumber(1) === 'number');
+  });
+
+  it('Should reverse 45 to 54', () => {
+    expect(reverseNumber(45)).toEqual(54);
+  });
+
+  it('Should reverse -2 to -2', () => {
+    expect(reverseNumber(-2)).toEqual(-2);
+  });
+
+  it('Should reverse -1234567 to -7654321', () => {
+    expect(reverseNumber(-1234567)).toEqual(-7654321);
+  });
+
+  it('Should throw error for invalid argument', () => {
+    expect(() => reverseNumber('hello')).toThrow('Invalid Argument');
+  });
+});