Discover the Magic of Reversing Integers in JavaScript with These Jaw-Dropping Code Examples

Table of content

  1. Why reverse integers?
  2. Reversing integers using a for loop
  3. Reversing integers using recursion
  4. Adding reversed digits
  5. Reversing binary digits
  6. Bonus: Reversing floats
  7. Conclusion

Why reverse integers?

Reversing integers can be a useful technique in programming for a variety of reasons. One common use case is when dealing with numbers that are input by a user or read in from an external source. In such cases, it may be necessary to reverse the digits of the number in order to perform certain calculations or manipulations.

Another reason for reversing integers is to generate palindromic numbers, which are numbers that read the same forwards and backwards. Palindromic numbers have a variety of interesting mathematical properties, and are often used in puzzles and games.

Reversing integers can also be useful when working with large numbers or arrays of numbers, as it can allow for more efficient sorting and searching algorithms. By reversing the order of the digits, the numbers can be sorted or searched more easily, making it faster and more efficient to perform the desired operations.

Overall, the ability to reverse integers is an essential skill for any programmer working with numerical data, and can open up a wide range of possibilities for manipulating and analyzing numbers in a variety of ways.

Reversing integers using a for loop

To reverse integers using a for loop in JavaScript, first we need to convert the integer into a string. This can be done using the toString() method. Once converted, we can use a for loop to iterate over the string in reverse order.

Here's an example:

let num = 12345;
let stringNum = num.toString();
let reversedNum = '';

for (let i = stringNum.length - 1; i >= 0; i--) {
  reversedNum += stringNum[i];

console.log(reversedNum); // Output: "54321"

In this example, we first convert the integer num into a string using the toString() method. We declare a variable reversedNum and assign an empty string to it. Then, we use a for loop to iterate over each character in stringNum, starting from the end of the string and moving backwards.

Inside the loop, we concatenate each character to the reversedNum variable using the += operator. Once the loop is finished, the reversedNum variable contains the reversed integer as a string.

Finally, we use the console.log() method to output the reversed integer to the console.

Using a for loop to reverse integers in JavaScript is a straightforward and efficient approach that can be used in a wide range of programming applications. By understanding the basics of for loops and string manipulation, developers can easily incorporate this technique into their JavaScript code.

Reversing integers using recursion

is a popular method for manipulating integers in JavaScript. Recursion is a function that calls itself repeatedly until a certain condition is met. When used to reverse an integer, this function takes the last digit of the integer and passes the remaining digits to another instance of the function. Each subsequent call adds the last digit to the growing reversed integer until no more digits remain.

Here is an example of how to reverse an integer using recursion:

function reverseInteger(num) {
  if (num < 0) {
    return -1 * reverseInteger(-num);
  if (num < 10) {
    return num;
  const lastDigit = num % 10;
  const remainingDigits = Math.floor(num / 10);
  const reversedDigits = reverseInteger(remainingDigits);
  return parseInt(`${lastDigit}${reversedDigits}`, 10);

This function first checks if the integer is negative and handles the sign accordingly. It then checks if the integer has only one digit, in which case it simply returns the integer. If there are more than one digit, the last digit is extracted and the remaining digits are passed to the function recursively. Finally, the last digit is appended to the reversed integer using string concatenation.

In conclusion, in JavaScript is a powerful technique for manipulating integers. While recursion can be difficult to understand at first, it is a valuable tool in a programmer's arsenal. By breaking down the problem into smaller, simpler sub-problems, it simplifies the task of reversing integers and other complex operations on integers.

Adding reversed digits

To add reversed digits in JavaScript, we first need to understand how to reverse an integer. This can be done using a combination of the modulus operator (%) and the floor division operator (//).

Here's an example of a function that reverses an integer:

function reverseInt(num) {
  let reversed = 0;
  while (num !== 0) {
    reversed = (reversed * 10) + (num % 10);
    num = Math.floor(num / 10);
  return reversed;

Once we have a function that can reverse an integer, adding the reversed digits is simple. We can add the original integer and the reversed integer and return the result.

function addReversedDigits(num) {
  let reversed = reverseInt(num);
  let sum = num + reversed;
  return sum;

That's it! We now have a function that can add the reversed digits of an integer.

It's worth noting that while the example function works for positive integers, it may not work as expected for negative integers. You may need to make some adjustments to handle negative numbers correctly.

Reversing binary digits

is a common operation when working with binary numbers. To reverse the binary digits of an integer in JavaScript, you can first convert the integer to its binary representation using the toString(2) method, which converts the integer to a string of binary digits. Once you have the binary representation of the integer, you can reverse the order of the digits using the split("") and reverse() methods, then join the reversed digits back into a string and convert the result back to an integer using the parseInt() method.

Here's an example code snippet to reverse the binary digits of an integer:

function reverseBinary(num) {
  let binary = num.toString(2);
  let reversed = binary.split("").reverse().join("");
  return parseInt(reversed, 2);

console.log(reverseBinary(5)); // Expected output: 10

In this example code, we define a function reverseBinary that takes an integer parameter num. We first use the toString(2) method to convert num to its binary representation and store the result in a variable binary. We then split the binary string into an array of individual digits using the split("") method, reverse the order of the digits using the reverse() method, and join the reversed digits back into a string using the join("") method. Finally, we use the parseInt() method to convert the reversed binary string back into an integer and return it.

When we call reverseBinary(5), the function returns 10, which is the integer with its binary digits reversed from 101 to 010.

Bonus: Reversing floats

Reversing floats involves reversing the digits after the decimal point. This can be achieved by first converting the float into a string, splitting the string at the decimal point, reversing the second part of the split string (i.e., the digits after the decimal point), and then joining the two split parts.

Here is an example code snippet that demonstrates this process:

function reverseFloat(n) {
  let str = n.toString();
  let parts = str.split('.');
  let reversed = parts[1].split('').reverse().join('');
  let result = parseFloat(`${parts[0]}.${reversed}`);
  return result;

console.log(reverseFloat(1234.5678)); // Outputs: 4321.8765

In this example, the reverseFloat() function takes a float as its parameter, converts it into a string using the toString() method, splits the string at the decimal point using the split() method, reverses the second part of the split string using the reverse() method, joins the two split parts using the join() method, and finally converts the resulting string back into a float using the parseFloat() method.

Overall, reversing floats is a relatively simple process that follows the same general principles as reversing integers. By breaking the float down into its component parts (i.e., the digits before and after the decimal point), it becomes straightforward to manipulate and reverse the digits as needed.


In , reversing integers in JavaScript is a simple yet powerful programming technique that can be useful in a variety of applications. By using the built-in reverse method in the Array object, you can easily reverse the order of a sequence of integers. This technique can be particularly useful in situations where you need to manipulate the order of items in an array, such as when sorting or searching.

One important thing to keep in mind when reversing integers in JavaScript is that the original array is modified in place. This means that if you need to preserve the original ordering of the array, you will need to create a separate copy of the array before applying the reverse method.

Overall, mastering the art of reversing integers is an important skill for any JavaScript programmer. By incorporating this technique into your programming toolbox, you can increase the versatility and power of your code, and achieve amazing results with ease. So why not give it a try today and experience the magic of reversing integers for yourself?

As a seasoned software engineer, I bring over 7 years of experience in designing, developing, and supporting Payment Technology, Enterprise Cloud applications, and Web technologies. My versatile skill set allows me to adapt quickly to new technologies and environments, ensuring that I meet client requirements with efficiency and precision. I am passionate about leveraging technology to create a positive impact on the world around us. I believe in exploring and implementing innovative solutions that can enhance user experiences and simplify complex systems. In my previous roles, I have gained expertise in various areas of software development, including application design, coding, testing, and deployment. I am skilled in various programming languages such as Java, Python, and JavaScript and have experience working with various databases such as MySQL, MongoDB, and Oracle.
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