Change every letter to next letter - JavaScript

We are required to write a JavaScript function that takes in a string and changes every letter of the string from the English alphabets to its succeeding element.

For example: If the string is ?

const str = 'how are you';

Then the output should be ?

const output = 'ipx bsf zpv';

How It Works

The algorithm processes each character by checking if it's a letter using ASCII codes. For letters 'a-y' and 'A-Y', it moves to the next letter. For 'z' and 'Z', it wraps around to 'a' and 'A' respectively. Non-alphabetic characters remain unchanged.

Example

Following is the code ?

const str = 'how are you';

const isAlpha = code => (code >= 65 && code <= 90) || (code >= 97 && code <= 122);
const isLast = code => code === 90 || code === 122;

const nextLetterString = str => {
    const strArr = str.split('');
    return strArr.reduce((acc, val) => {
        const code = val.charCodeAt(0);
        if(!isAlpha(code)){
            return acc+val;
        };
        if(isLast(code)){
            return acc+String.fromCharCode(code-25);
        };
        return acc+String.fromCharCode(code+1);
    }, '');
};

console.log(nextLetterString(str));

Output

Following is the output in the console ?

ipx bsf zpv

Key Points

• ASCII codes: 'A-Z' are 65-90, 'a-z' are 97-122
• Wrap-around: 'z' becomes 'a', 'Z' becomes 'A'
• Non-letters preserved: Spaces and punctuation remain unchanged

Alternative Approach Using String Methods

const nextLetterStringSimple = str => {
    return str.split('').map(char => {
        if (/[a-y]/i.test(char)) {
            return String.fromCharCode(char.charCodeAt(0) + 1);
        } else if (char === 'z') {
            return 'a';
        } else if (char === 'Z') {
            return 'A';
        }
        return char;
    }).join('');
};

console.log(nextLetterStringSimple('xyz ABC'));

yza BCD

Conclusion

This function effectively shifts each letter to the next in the alphabet using ASCII manipulation. The wrap-around logic ensures 'z' becomes 'a' and 'Z' becomes 'A' for complete alphabet cycling.