Second version of the Currency Converter that worked.

newSolution.js

let input = require('sync-input');

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("What do you want to convert?");

let fromCurrency = input("From:");

let currencies = [
  {
    name: "JPY",
    val: 113.5,
  },
  {
    name: "EUR",
    val: 0.89,
  },
  {
    name: "RUB",
    val: 74.36,
  },
  {
    name: "GBP",
    val: 0.75,
  },
  {
    name: "USD",
    val: 1,
  },
];

(function checkCurrency(fCurr) {
  let isFound = false;
  let fromCurrVal;
  let currArray;
  
  currencies.forEach(function(itm, ind, arr) {
    if(itm.name == fCurr) {
      // true
      isFound = true;
      fromCurrVal = itm.val;
      currArray = arr;
    }
  });
  
  (!(isFound == true)) ? console.log("Unknown currency") : convertCurrency(fromCurrVal, currArray);
}(fromCurrency.toUpperCase()));

function convertCurrency(fCurrVal, currArr) {
  let isFound = false;
  let toCurrency = input("To:");
  let toCurrVal;
  
  currArr.forEach(function(item) {
    if(item.name == toCurrency.toUpperCase()) {
      // true
      isFound = true;
      toCurrVal = item.val;
    }
  });
  
  let amount;
  let result;
  
  if(!(isFound == true)) {
    result = "Unknown currency";
  } else {
    amount = input("Amount:");
    
    if(amount < 1) {
      result = "The amount can not be less than 1";
    } else if(isNaN(amount)) {
      result = "The amount has to be a number";
    } else {
      // all tests passed. Go ahead.
      result = amount * toCurrVal / fCurrVal;
    }
  }
  
  isNaN(result) ? console.log(result) : console.log("Result: " + amount + " " + fromCurrency.toUpperCase() + " equals " + parseFloat(result).toFixed(4) + " " + toCurrency.toUpperCase());
}