JavaScript Program to Check Evil Number

Posted in JavaScript Tutorial

Updated on Jan 11, 2024

By Mari Selvan

👁️ 46 - Views

⏳ 4 mins

💬 1 Comment

Photo Credit to CodeToFun

🙋 Introduction

In the realm of programming, understanding the properties of numbers is a fascinating journey. One interesting concept is that of Evil Numbers.

An Evil Number is a non-negative integer that has an even number of '1' bits in its binary representation.

In this tutorial, we will explore a JavaScript program designed to check whether a given number is an Evil Number.

The program involves converting the decimal number to its binary representation and counting the number of '1' bits.

📄 Example

Let's delve into the JavaScript code that accomplishes this task.

isEvilNumber.js

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// Function to count the number of set bits (1s) in binary representation
function countSetBits(number) {
  let count = 0;

  while (number) {
    count += number & 1;
    number >>= 1;
  }

  return count;
}

// Function to check if a number is an Evil Number
function isEvilNumber(number) {
  // Count the number of set bits in the binary representation
  const setBitsCount = countSetBits(number);

  // If the count of set bits is even, it is an Evil Number
  return setBitsCount % 2 === 0;
}

// Driver program
// Replace this value with the number you want to check
const number = 15;

// Call the function to check if the number is an Evil Number
if (isEvilNumber(number))
  console.log(`${number} is an Evil Number.`);
else
  console.log(`${number} is not an Evil Number.`);

💻 Testing the Program

To test the program with different numbers, modify the value of number in the code.

Output

15 is an Evil Number.

Run the script to check if the specified number is an Evil Number.

🧠 How the Program Works

The program defines a function countSetBits that takes a number as input and returns the count of set bits (1s) in its binary representation.
The function isEvilNumber checks if the count of set bits is even, indicating that the number is an Evil Number.
Replace the value of number in the main program with the desired number you want to check.
The program calls the isEvilNumber function and logs the result to the console.

📏 Between the Given Range

Let's explore the javascript code that checks for Evil Numbers in the specified range.

isEvilNumber.js

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// Function to check if a number is Evil
function isEvilNumber(num) {
  // Convert the number to binary
  const binaryRepresentation = num.toString(2);

  // Count the number of '1' bits
  const countOnes = binaryRepresentation.split('1').length - 1;

  // Check if the count of '1' bits is even (Evil Number)
  return countOnes % 2 === 0;
}

// Function to find Evil Numbers in a specified range
function findEvilNumbersInRange(start, end) {
  const evilNumbers = [];

  for (let i = start; i <= end; i++) {
    if (isEvilNumber(i)) {
      evilNumbers.push(i);
    }
  }

  return evilNumbers;
}

// Driver program
// Define the range
const startRange = 1;
const endRange = 10;

// Call the function to find Evil Numbers in the range
const evilNumbersInRange = findEvilNumbersInRange(startRange, endRange);

// Output the results
console.log(`Evil numbers in the range ${startRange} to ${endRange}:`);
console.log(evilNumbersInRange.join(' '));

💻 Testing the Program

The provided code is configured to find Evil Numbers in the range from 1 to 10. You can adjust the range by modifying the values of startRange and endRange.

Output

Evil numbers in the range 1 to 10:
3 5 6 9 10

Run the script to see the Evil Numbers within the specified range.

🧠 How the Program Works

The program defines a function isEvilNumber to check if a given number is an Evil Number.
Inside the function, it converts the number to its binary representation and counts the number of '1' bits.
The findEvilNumbersInRange function iterates through the specified range, calling isEvilNumber for each number, and collects Evil Numbers.
The driver program defines the range from 1 to 10, calls the function, and outputs the Evil Numbers.

🧐 Understanding the Concept of Evil Number

Before delving into the code, let's understand the concept of Evil Numbers. An Evil Number is a non-negative integer that has an even number of '1' bits in its binary representation.