number-system-converter/index.js

const readline = require('readline').createInterface({
    input: process.stdin,
    output: process.stdout
});

function dec_to_base() {
    readline.question(`Enter a number to convert: `, num => {
        num = parseInt(num);
        readline.question(`Enter a number new base: `, base => {
            base = parseInt(base);
            try {
                new_num = num.toString(base);
                console.log(`\nBASE 10: ${num} ==> BASE ${base}: ${new_num}`);
            } catch (RangeError) {
                console.log(`Base is not in the range of 2 to 36.\nExiting...`);
            } finally {
                readline.close();
            };
        });
    });
};

function base_to_dec() {
    readline.question(`Enter a number to convert: `, num => {
        readline.question(`Enter the number's base: `, base => {
            base = parseInt(base);
            try {
                new_num = parseInt(num, base);
                console.log(`\nBASE ${base}: ${num} ==> BASE 10: ${new_num}`);
            } catch (RangeError) {
                console.log(`Base is not in the range of 2 to 36.\nExiting...`);
            }
            finally {
                readline.close();
            };
        });
    });
};

function base_to_base() {
    readline.question(`Enter a number to convert: `, num => {
        readline.question(`Enter the number's base: `, base => {
            base = parseInt(base);
            readline.question(`Enter a number new base: `, new_base => {
                new_base = parseInt(new_base);
                try {
                    let dec_num = parseInt(num, base);
                    let new_num = dec_num.toString(new_base);
                    console.log(`\nBASE ${base}: ${num} ==> BASE ${new_base}: ${new_num}`);
                } catch (RangeError) {
                    console.log(`One or more bases is not in the range of 2 to 36.\nExiting...`);
                }
                finally {
                    readline.close();
                };
            });
        });
    });
};

readline.question(`Choose an option:\n\n1) decimal to any base\n2) any base to decimal\n3) any base to any base\n`, choice => {
    if (choice * 1.0) {
        choice = parseInt(choice);
        switch (choice) {
            case 1:
                dec_to_base();
                break;
            case 2:
                base_to_dec();
                break;
            case 3:
                base_to_base();
                break;
            default:
                console.log("Please choose a proper entry.");
                readline.close();
                break;
        };
    } else {
        console.log("Please enter a number.");
        readline.close();
    };
});