User Input Node.js

const readline = require('readline').createInterface({
  input: process.stdin,
  output: process.stdout
});
const run_questions = () => {
  readline.question('Enter a number ', num1 => {
    readline.question('Enter a second number ', num2 => {
      const num2Parsed = Number.parseInt(num2)
      const num1Parsed = Number.parseInt(num1)
      const sumParsed = num1Parsed + num2Parsed
      if(!Number.isNaN(num1Parsed) && !Number.isNaN(num2Parsed)) {
        console.log(`${num1Parsed} + ${num2Parsed} = ${sumParsed}`);
        readline.close()
      } else  {
        console.log(`You failed to enter a valid number, please try again.`);
        run_questions()
      }
    })
  });
};

run_questions()