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JavaScript: Reverse a number

JavaScript Function: Exercise-1 with Solution

Write a JavaScript function that reverse a number.
Sample Data and output:
Example x = 32243;
Expected Output: 34223

Pictorial Presentation:

JavaScript: Reverse a number

Sample Solution:

HTML Code:

<!DOCTYPE html>
<html>
<head>
<meta charset=utf-8 />
<title>Reverse a number</title>
</head>
<body>
  
</body>
</html>

JavaScript Code:

function reverse_a_number(n)
{
	n = n + "";
	return n.split("").reverse().join("");
}
console.log(Number(reverse_a_number(32243)));

Sample Output:

34223

Explanation:
Assume n = 1000.
Convert a number to a string :
Code : -> n = n + "";
Note : There are different ways to convert number to string :

  • String literal -> str = "" + num + "";
  • String constructor -> str = String(num);
  • toString -> str = num.toString();
  • String Literal simple -> str = "" + num;

The split() method is used to split a String object into an array of strings by separating the string into substrings.
Code : console.log('1000'.split(""));
Output : ["1", "0", "0", "0"]

The reverse() method is used to reverse an array in place. The first array element becomes the last and the last becomes the first.
Code : console.log(["1", "0", "0", "0"].reverse());
Output : ["0", "0", "0", "1"]

The join() method is used to join all elements of an array into a string.
Code : console.log(["1", "0", "0", "0"].reverse().join(""));
The Number constructor contains constants and methods for working with numbers. Values of other types can be converted to numbers using the Number() function.
Output : 1

Flowchart:

Flowchart: JavaScript function: Reverse a number

Live Demo:

See the Pen JavaScript -Reverse a number-function-ex- 1 by w3resource (@w3resource) on CodePen.


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Next: Write a JavaScript function that checks whether a passed string is palindrome or not?

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JavaScript: Tips of the Day

How to check whether a string contains a substring in JavaScript?

ECMAScript 6 introduced String.prototype.includes:

const string = "foo";
const substring = "oo";

console.log(string.includes(substring));

includes doesn't have Internet Explorer support, though. In ECMAScript 5 or older environments, use String.prototype.indexOf, which returns -1 when a substring cannot be found:

var string = "foo";
var substring = "oo";

console.log(string.indexOf(substring) !== -1);

Ref: https://bit.ly/3fFFgZv