JavaScript Program to Test if Kth Character is Digit in String

In this article, we are Given a String, we will check if the K^th index element is a digit or not. If it is a digit then we will print true else we will print false.

Examples:

Input : test_str = ‘geeks9geeks’, K = 5 
Output : True 
Explanation : 5th idx element is 9, a digit, hence True.
Input : test_str = ‘geeks9geeks’, K = 4 
Output : False 
Explanation : 4th idx element is s, not a digit, hence False. 

These are the following approaches by using these we can check whether the digit is present at the K^th index or not:

Using charAt():

In this approach, we check if the character at the Kth index in a string is a digit. It uses the ‘charAt’ method to retrieve the character at the specified index and the ‘includes’ method to check if the character exists in the numeric string “0123456789”. The result is a boolean indicating whether the Kth element is a digit in the string.

Example: This example shows the use of the above-explained approach.

Javascript

// Initializing string
let test_str = 'geeksgeeks';

// Printing original string
console.log("The original string is : " + test_str);

// initializing K
let K = 5;

// Checking if Kth character is a
// digit in the string

// Getting numeric string
let num_str = "0123456789";
let res = num_str.includes(test_str.charAt(K));

// Printing result
console.log("Is Kth element String : " + res);

Output

The original string is : geeksgeeks
Is Kth element String : false

Using regular expression:

In this approach, we are using the ‘match’ method to check if the character at the K^thj index in a string matches the regular expression pattern for a single digit `\d`. It stores the result in a boolean variable ‘res’ using the double negation ‘!!’ to convert the match result to a boolean value. Finally, it prints whether the K^th element is a digit in the string.

Example: This example shows the use of the above-explained approach.

Javascript

// Initialize string
let test_str = 'geeks4geeks';

// Print original string
console.log("The original string is : " + test_str);

// Initialize K
let K = 5;

// Regular expression pattern for a single digit
let pattern = /\d/;

// Check if the Kth character
// matches the pattern
let match = test_str.charAt(K).match(pattern);

// Set the value of res based on the match result
let res = !!match;

// Print result
console.log("Is Kth element String : " + res);

Output

The original string is : geeks4geeks
Is Kth element String : true