recursive function returning undefined javascript

Question

I am trying to create a caesar cypher, I know this might not be the best or easiest way to do it but I created a recursive function that loops over adding numbers to each character in order to change it to a different character, but when I run my code instead of getting a character as an answer I get undefined

'''

const caesar = function(inputString, shiftNo) {
    let outputString = "";
    for (let i = 0; i < inputString.length; i++){
        let unicodeCode = inputString.charCodeAt(i);

        if ( unicodeCode <= 90 && unicodeCode >= 65 || unicodeCode <= 122 && unicodeCode >= 97){
            outputString += recCounter(unicodeCode, shiftNo);
        }
        else{
            outputString += inputString.charAt(i);
        }
    }
    return outputString;
}

function recCounter(unicodeCode, shiftNo){
    let shiftedUniCode = unicodeCode;
    let substractedShiftNum = shiftNo;
    if (shiftedUniCode === 123){
        shiftedUniCode = 97;
    }
    else if (shiftedUniCode === 91){
        shiftedUniCode = 65;
    }
    if (shiftNo === 0){
        return String.fromCharCode(shiftedUniCode);
    }
    else {
        recCounter(shiftedUniCode + 1, substractedShiftNum - 1);
    }
}

'''

I have tried changing the parameters and the way the recursive function works but all I get is undefined when I run my code

@pointy there already is a return when the variable "shiftNo" equals zero — Rios
– Rios, Commented Feb 10, 2020 at 20:02
In the else clause, it should be: return recCounter(...). Without that return statement, your function returns undefined, not the result of your recursive call. — triangle_man
– triangle_man, Commented Feb 10, 2020 at 20:05
@Rios A function only returns to its callee, one step. The return is then not use, aka dead code, and there is always an invisible line saying return undefined; in all functions so when you don't return anything JS does. — Sylwester
– Sylwester, Commented Feb 10, 2020 at 20:10

tstoev · Accepted Answer · 2020-02-10 20:04:39Z

1

you skipped the return on the recursive call
change:

recCounter(shiftedUniCode + 1, substractedShiftNum - 1);

to:

 return recCounter(shiftedUniCode + 1, substractedShiftNum - 1);

answered Feb 10, 2020 at 20:04

tstoev

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