function myDisplayer(some) {
    // eslint-disable-next-line no-undef
    document.getElementById('demo').innerHTML = some;
}

function myCalculator(num1, num2, myCallback) {
    const sum = num1 + num2;
    myCallback(sum);
}

myCalculator(5, 5, myDisplayer);

function myDisplayer(some) {
    document.getElementById('demo').innerHTML = some;
}

function getFile(myCallback) {
    const req = new XMLHttpRequest();
    req.open('GET', 'mycar.html');
    req.onload = function () {
        if (req.status == 200) {
            myCallback(this.responseText);
        } else {
            myCallback(`Error: ${req.status}`);
        }
    };
    req.send();
}

getFile(myDisplayer);