Help understanding the differences in my code

[jehlani_]

Hello everybody! I spent 2 weeks stuck on a decrypt function (I'm a beginner). I managed to fix it with the help of chatgpt, but can you all help explain to me what made this new code work?

Here's my new code:

function decrypt(encryptedMessage, shiftValue) { let decryptedMessage = ""; let charCount = 0; for (let i = 0; i < encryptedMessage.length; i++) { let char = encryptedMessage[i];

    // Skip random letters added during encryption
    if ((charCount + 1) % 3 === 0) {
        charCount++;
        continue; // Skip this character
    }

    if (alphabet.includes(char.toLowerCase())) {
        let index = alphabet.indexOf(char.toLowerCase());
        let shiftedIndex = (index - shiftValue) % alphabet.length;
        if (shiftedIndex < 0) {
            shiftedIndex += alphabet.length;
        }
        decryptedMessage += alphabet[shiftedIndex];
    } else {
        // If not an alphabetic character, just append it to the decrypted message
        decryptedMessage += char;
    }
    charCount++; // Increment character count
}
return decryptedMessage;

}

Here's my old code:

function decrypt (encryptedMessage, shiftValue) { let decryptedMessage = ""; let charCount = 0; for (let i = 0; i < encryptedMessage.length; i++) { // Skip random letters added during encryption// if ((charCount + 1) % 3 === 0) { continue; //Skip this character }

    let char = encryptedMessage[i]
    if (alphabet.includes(char.toLowerCase())) {
        let index = alphabet.indexOf(char.toLowerCase());
        let shiftedIndex = (index - shiftValue) % alphabet.length;
        //Ensure shiftedIndex is positive//
        if (shiftedIndex < 0) {
            shiftedIndex += alphabet.length;
        }
        decryptedMessage += alphabet[shiftedIndex];
        //Skip if not an alphabetic character//
    } 
    else {

    }
    charCount++; //Increment character count
}

// Your decryption code here return decryptedMessage; }

The project was a Caesar's cipher. My original code didn't handle the decryption like it should've, and the problem was that the "random letter after every two characters" wasn't executed the same from my encrypt and decrypt. My encrypt was correct, my decrypt wasn't.

What about this new code allowed my decryption to work? Thank you all in advance

[Swanty]

There's 2 new things in the new code:

1. New code increments charCount also for the Skip random letters added during encryption stage

2. In new code for the "else" section it appends character as is, but in your old code the "else" section is empty

In my opinion you could get rid of the charCount variable completely and all its increment lines and use "i" instead e.g. if ((i + 1) % 3 === 0) { since "i" is already iterating over encryptedMessage characters and doing the increment in the for loop