Why my google sheets custom function doesn't work with arrayformula?

Question

I'm building a custom function using decodeuricomponent and handling URIError: malformed URI with "try/catch". It was fine until I had to change the code to work with arrayformula (built-in function).

I've already tried several ways to do it, but none of them worked.

The else part works fine, but when it's an array (always true when arrayformula is used) returns encodedString.map(row => row.map(cell => unescape(cell))) to all cells.

I need a solution that works on a cell level (every array position separately) even when I use arrayformula.

My Script

function stringDecoder(encodedString) {
  if(Array.isArray(encodedString)===true){
    try{
      return encodedString.map(row => row.map(cell => decodeURIComponent(cell)))
    }
    catch(err){
      return encodedString.map(row => row.map(cell => unescape(cell)))
    }
  }
  else{
    try{
      return decodeURIComponent(encodedString)
    }
    catch(err){
      return unescape(encodedString)
    }
  }
}

Answer 1

Try modifying the loop like this, so it applies the try/catch to each cell individually:

function stringDecoder(encodedString) {
  if (Array.isArray(encodedString)) {
    return encodedString.map(row => row.map(cell => {
      try {
        return decodeURIComponent(cell);
      } catch (err) {
        return unescape(cell);
      }
    }));
  } else {
    try {
      return decodeURIComponent(encodedString);
    } catch (err) {
      return unescape(encodedString);
    }
  }
}