Javascript reverse alphabet

Question

so I've been messing around with the .replace() function lately and wanted to make it reverse whatever the user inputs. (Aka a -> z, A -> Z, b -> y, B -> Y, ...)

I'm using function stacking, so I just added .replace().replace()... for every letter, but of course that won't work since whenever it hits n, it will begin to reverse all the progress and I end up with an inaccurate translation. Any idea how I can work around this, since as far as I know, JS doesn't have a .reverse() function like Python?

In case you need it, here's my code

//replacing letters
lettertext = ttext.replace("a", "z")
.replace("A", "Z")
.replace("b", "y")
.replace("B", "y")
.replace("c", "x")
.replace("C", "X")
.replace("d", "w")
.replace("D", "W")
.replace("e", "v")
.replace("E", "V")
.replace("f", "u")
.replace("F", "U")
.replace("g", "t")
.replace("G", "T")
.replace("h", "s")
.replace("H", "S")
.replace("i", "r")
.replace("I", "R")
.replace("j", "q")
.replace("J", "Q")
.replace("k", "p")
.replace("K", "P")
.replace("l", "o")
.replace("L", "O")
.replace("m", "n")
.replace("M", "N")
.replace("n", "m")
.replace("N", "M")
.replace("o", "l")
.replace("O", "L")
.replace("p", "k")
.replace("P", "K")
.replace("q", "j")
.replace("Q", "J")
.replace("r", "i")
.replace("R", "I")
.replace("s", "h")
.replace("S", "H")
.replace("t", "g")
.replace("T", "G")
.replace("u", "f")
.replace("U", "F")
.replace("v", "e")
.replace("V", "E")
.replace("w", "d")
.replace("W", "D")
.replace("x", "c")
.replace("X", "C")
.replace("y", "b")
.replace("Y", "B")
.replace("z", "a")
.replace("Z", "A")
.replace("ä", "ß")
.replace("Ä", "ẞ")
.replace("ö", "ü")
.replace("Ö", "Ü")
.replace("ü", "ö")
.replace("Ü", "Ö")
.replace("ß", "ä")
.replace("ẞ", "Ä")

Answer 1

Just create an array consisting of string characters from a - z and another array consisting of all the 8 umlaut characters that you mentioned.

You can now simply create a reusable function say, reverseChar() that accepts a character as a parameter.

The function can then check if the inputted character is an alphabet or an umlaut character using a basic regex tester.

The function then tries to match the inputted character with the string characters from the respective array and if there is a match, return the same indexed character from the array reversed.

---

Try inputting any character from a-z, A-Z or one of the umlaut characters mentioned above in the code snippet below to see how it works:

var alpha = ["a","b","c","d","e","f","g","h","i","j","k","l","m","n","o","p","q","r","s","t","u","v","w","x","y","z"];
var umlauts = ["ä","Ä","ö","Ö","ü","Ü","ß","ẞ"]

var val = "";

var result = document.getElementById("result");

function reverseChar(x) {
    
    if (/^[a-zA-Z]+$/.test(x)) {
      for (i = 0; i < 26; i++) {
          if (x.toLowerCase() == alpha[i]) {
              if (x == x.toUpperCase()) {
                val = ((alpha.reverse())[i]).toUpperCase();
              } else {
                val = (alpha.reverse())[i];
              }
          }
      }
	  result.innerHTML = `The reversed character for <strong>${x}</strong> is <strong>${val}</strong>`;
    } else {
        for (i = 0; i < umlauts.length; i++) {
        	if (x == umlauts[i]) {
            val = (umlauts.reverse())[i];
          }
        }
        result.innerHTML = `The reversed character for <strong>${x}</strong> is <strong>${val}</strong>`;
    }
}

// JavaScript below is for the HTML Example

var btn = document.getElementById("btn");

function checkChar(){
    var char = document.getElementById("char");
    var input = char.value;
    reverseChar(input);
}

btn.addEventListener("click", checkChar);

<input id="char" type="text" maxlength="1" />
<button type="button" id="btn">Check reversed character</button>
<p id="result"></p>