var baseInput = document.querySelector('#base');
var heightInput = document.querySelector('#height');
var areaInput = document.querySelector('#area');
var calcButton = document.querySelector('#calcButton');

if(calcButton) {
    calcButton.addEventListener('click', () => {
        workInput();
    });    
}

function workInput() {
    let baseGood = checkInput(baseInput.value);
    let heightGood = checkInput(heightInput.value);
    if (baseGood && heightGood) {
        let base = Number(baseInput.value);
        let height = Number(heightInput.value);
        let area = calcTriangleArea(base, height);
        areaInput.value = area + " cm²";        
    }else {
        alert('Hiba!')
    }

}

function calcTriangleArea(base, height) {
    return base * height / 2;
}

function checkInput(input) {
    if(input<1) {
        throw new Error('Hiba! 1-nél kisebb érték!')
    }
    let res = input.match(/^[0-9]+$/);
    if(res) {
        return true;
    }else {
        return false;
    }
}