LuisAFK

function y(b){return(b-32)*5/9}function z(b){return b*9/5+32}function A(b){return b-273.15}function B(b){return b+273.15}for await(let b of console){if(!b||b==="exit")break;const[,q,w,x]=b.match(/(\d+(?:\.\d+)?)\s*([fkc])\s*(?:in|to)\s*([fkc])/i)||[];if(!q||!w||!x){console.log("Invalid input");continue}const j=parseFloat(q);let g;switch(w.toLowerCase()+x.toLowerCase()){case"fc":g=y(j);break;case"cf":g=z(j);break;case"kc":g=A(j);break;case"ck":g=B(j);break;default:console.log("Invalid conversion");continue}console.log(g)}
Into this:

function convertFahrenheitToCelsius(fahrenheitTemperature) {
  return ((fahrenheitTemperature - 32) * 5) / 9;
}

function convertCelsiusToFahrenheit(celsiusTemperature) {
  return (celsiusTemperature * 9) / 5 + 32;
}

function convertKelvinToCelsius(kelvinTemperature) {
  return kelvinTemperature - 273.15;
}

function convertCelsiusToKelvin(celsiusTemperature) {
  return celsiusTemperature + 273.15;
}

for await (let consoleLogEntries of console) {
  if (!consoleLogEntries || consoleLogEntries === "exit") break;

  const [, temperatureValue, matchedTemperatureValue, matchedTemperature] =
    consoleLogEntries.match(
      /(\d+(?:\.\d+)?)\s*([fkc])\s*(?:in|to)\s*([fkc])/i,
    ) || [];

  if (!temperatureValue || !matchedTemperatureValue || !matchedTemperature) {
    console.log("Invalid input");
    continue;
  }

  const parsedTemperature = parseFloat(temperatureValue);
  let g;

  switch (
    matchedTemperatureValue.toLowerCase() + matchedTemperature.toLowerCase()
  ) {
    case "fc":
      g = convertFahrenheitToCelsius(parsedTemperature);
      break;

    case "cf":
      g = convertCelsiusToFahrenheit(parsedTemperature);
      break;

    case "kc":
      g = convertKelvinToCelsius(parsedTemperature);
      break;

    case "ck":
      g = convertCelsiusToKelvin(parsedTemperature);
      break;

    default:
      console.log("Invalid conversion");
      continue;
  }

  console.log(g);
}