Continuous RGBA to HEXA converter

rgbaToHex.js

const readline = require('readline');

function colorToHex(rgb) {
    let hex = Number(rgb).toString(16);
    if (hex.length < 2) {
        hex = `0${hex}`;
    }
    return hex;
};

function alphaToHex(alpha) {
    const preHex = Math.round(alpha * 255);
    const hex = (preHex + 0x10000).toString(16).substr(-2).toUpperCase();
    return hex;
}

function rgbaToHex(r, g, b, a) {
    const red = colorToHex(r);
    const green = colorToHex(g);
    const blue = colorToHex(b);

    if (a === '1' || a === '0') {
        return red + green + blue;
    }

    const alpha = alphaToHex(a);
    return red + green + blue + alpha;
}


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

function askToConvert() {
    rl.question('RGBA: ', (answer) => {

        if (answer === 'exit') rl.close();

        const withoutSpaces = answer.replace(/\s/g, '').replace(/rgba\(/g, '').replace(/\)/g, '');
        const prepared = withoutSpaces.split(',');
        const [r, g, b, a] = prepared;

        const hex = rgbaToHex(r, g, b, a);
        console.log(`#${hex}`);

        askToConvert();
    });
}

askToConvert();