JavaScript Program to Check if a String Contains only Alphabetic Characters

In this article, we are going to learn about checking if a string contains only alphabetic characters in JavaScript.Checking if a string contains only alphabetic characters means verifying that all characters within the string are letters of the alphabet (A-Z or a-z) and do not include any digits, symbols, or other non-alphabetic characters.

Some common methods can be used to check if a string contains only alphabetic characters in JavaScript, which are listed below:

We will explore all the above methods along with their basic implementation with the help of examples.

Approach 1: Using a Regular Expression

To check if a string contains only alphabetic characters in JavaScript, use the regular expression /^[a-zA-Z]+$/. It returns true if the string consists solely of letters, and false otherwise.

Syntax:

let regex = /^[a-zA-Z]+$/;

Example: In this example, the regular expression ^[a-zA-Z]+$ tests if a string consists only of alphabetic characters (letters). The code validates str1 as true and str2 as false.

Javascript

let str1 = "GeeksforGeeks";
let str2 = "Geeks123";

let regex = /^[a-zA-Z]+$/;

console.log(regex.test(str1));
console.log(regex.test(str2));

Output

true
false

Approach 2: Using for-of loop

In this approach, we are using for…of loop to iterate through each character in the input string. It returns true if all characters are alphabetic (A-Z or a-z), otherwise false.

Syntax:

for ( variable of iterableObjectName) {
   ...
};

Example: In this example, checkAlphabets function iterates through each character in the input string and returns true if all characters are alphabetic (A-Z or a-z), otherwise false.

Javascript

function checkAlphabets(input) {
    for (const char of input) {
        if (!(char >= "a" && char <= "z") &&
            !(char >= "A" && char <= "Z")) {
            return false;
        }
    }
    return true;
}

const str1 = "GeeksforGeeks";
const str2 = "Geeks123";

console.log(checkAlphabets(str1));
console.log(checkAlphabets(str2)); 

Output

true
false

Approach 3: Using every() method and charCodeAt() method

This approach converts the string into an array of characters using the spread operator ([...str]). It then uses the every method to check if every character has a Unicode code within the range of alphabetic characters.

Example: In this example, we are using every method and charCodeAt.

Javascript

function isAlphabetic(str) {
    const result = [...str]
        .every(char => (char >= 'a' && char <= 'z') 
                    || (char >= 'A' && char <= 'Z'));
    console.log(result);
    return result;
}

// Example usage
isAlphabetic("abc"); // true
isAlphabetic("123"); // false

Output

true
false

Approach 4: Using isNaN() function

In this Approach we iterates through each character of the string, checking if it’s not a number using isNaN(). It returns true if all characters are non-numeric, indicating the string contains only alphabetic characters.

Example : In this example we defines a function isAlphabetic to check if a string consists only of alphabetic characters using the isNaN function. It tests the function with two strings and prints the results.

JavaScript

let str1 = "GeeksforGeeks";
let str2 = "Geeks123";

function isAlphabetic(str) {
    return [...str].every(char => isNaN(char));
}

console.log(isAlphabetic(str1)); 
console.log(isAlphabetic(str2)); 

Output

true
false