currency-converter2.js

// import the readline module
let rl = require('readline').createInterface({
  input: process.stdin,
  output: process.stdout,
});

console.log("Welcome to Currency Converter!");
console.log(`1 USD equals  1 USD
1 USD equals  113.5 JPY
1 USD equals  0.89 EUR
1 USD equals  74.36 RUB
1 USD equals  0.75 GBP`);
console.log("I can convert USD to these currencies: JPY, EUR, RUB, USD, GBP");
console.log("Type the currency you wish to convert: USD");

// ask questions
rl.question("To which currency? ", (curr) => {
  // show currency
  console.log("To: > " + curr);
  rl.question("How much? ", (amnt) => {
    // show amount
    console.log("Amount: > " + amnt);
    rl.close();
    convertCurrency(curr, amnt);
  });
});

// function to convert currency
function convertCurrency(currency, amount) {
  let output;
  
  // run checks on the amount
  function checks(val) {
    // val; currency value
    if(amount < 1) {
      output = "The amount can not be less than 1";
    } else if(isNaN(amount)) {
      output = "The amount has to be a number";
    } else {
      output = amount * val;
    }
  }
  
  // find match among currencies
  if(currency == "JPY" || currency == "jpy") {
    checks(113.5);
  } else if(currency == "EUR" || currency == "eur") {
    checks(0.89);
  } else if(currency == "RUB" || currency == "rub") {
    checks(74.36);
  } else if(currency == "GBP" || currency == "gbp") {
    checks(0.75);
  } else if(currency == "USD" || currency == "usd") {
    checks(1);
  } else {
    output = "Unknown currency";
  }
  
  // show result
  isNaN(output) ? console.log(output) : console.log("Result: " + amount + " USD equals " + parseFloat(output).toFixed(4) + " " + currency);
}