Reverse a Number in Javascript

Introduction

We might come across a situation while coding where we have to reverse a number. There are many approaches that can be used to do our task. It may seem tricky, but in actuality, these approaches are pretty simple and can be implemented easily. Let's take a look at the most popular ways of creating new lines with JavaScript.

Algorithm to Reverse a Number

Basically, this approach works on the removal of the last digit of the number, and that last digit can be appended to the right of a new value. So let's see the steps for this algorithm:

• Iterate a loop until the number's value is greater than 0. 
• Iterate a loop until the number's value is greater than 0.  Set the result variable as 0.
• Use modulo to get the last digit of the number at each iteration.
• Multiply the result by ten and then add the modulo digit to it. 
• Replace the number with the floor(number/10) to remove the last digit of the number.

Let's take an example for reversing 12 so for that; we will initialize the result as 0 and start a loop. In the first iteration, we will take the modulo of 12 by 10 and divide 12 by 10 to get the value 2 and add this value to result variable's right, Now the result variable is 2, and the number to reverse is 1. In the next iteration by modulo, we will get 1 and will append the result to make the result variable 21. Hence, the number is reversed.

JavaScript Program to Reverse a Number

Now we know about the algorithm that will be used to reverse the number, now let's apply this algorithm to a JavaScript program:

Example

Output:

By Converting the Number to a String

We can convert the number to a string value, split the string value, and put all of the string's characters in an array, then, reverse the array and finally convert that array to a string by connecting all characters, and then finally convert that string back to a number. In JavaScript, this approach can be completed in only one line using the below 3 functions:

• split() for splitting the characters of the string value and adding them to an array
• reverse() for reversing the array values
• join() for finally joining all the array values to a string

Now let us see the JavaScript program for the above:

Example

Output:

Solving with an Arrow Function

Arrow functions can be used to make the above approach more concise and professional. Also, we can handle the case of reversing a negative number by explicitly checking the sign on the given number.

Now let's see the JavaScript program for the above:

Example

The arrow function makes the code concise and fast.

Output:

Solving with a Regular Function

Let's write a regular function for the above Arrow function that performs the same task as the above one. We have handled the case for reversing a negative number by explicitly checking the sign on the given number.

Now let's see the JavaScript program for the above:

Example

The arrow function makes the code concise and fast.

Output:

Difference Between an Arrow Function & Regular Function

In the above examples, the only difference between the Arrow Function and the Regular Function is that the Regular Function requires a return value, while the  Arrow functions have an implicit return value, and the value is returned according to the statements.