calculator.ts

// const readlineSync = require('readline-sync')

import { question } from 'readline-sync';

type Operator = '+' | '-' | '*' | '/';

const fNum: string = question('Enter first number: ');
const operator: string = question('Enter operator: '); // + , - , * , /
const sNum: string = question('Enter second number: ');

// console.log(fNum, operator, sNum);

let isInputValid : boolean = isNumber(fNum) && isOperator(operator) && isNumber(sNum);

let firstNumber = parseInt(fNum);
let secondNumber = parseInt(sNum);

if(isInputValid) {
    const result: number = calculate(firstNumber, operator as Operator, secondNumber);
    console.log(result);
} else {
    console.log('Invalid input');
}

function calculate(num1 : number, op: Operator, num2: number) : number {
    switch(op) {
        case '+':
            return num1+num2;
        case '-':
            return num1-num2;
        case '*':
            return num1*num2;
        case '/':
            return num1/num2;
    }
}

// console.log(isOperator(operator));

function isNumber (value: string) : boolean {
    let num = parseInt(value, 10);
    let notNumber = isNaN(num);
    return !notNumber;
}

function isOperator (value: string): boolean {
    switch(value) {
        case '+':
        case '-':
        case '*':
        case '/':
            return true;
        default:
            return false;
    }
}