const calcButton = document.querySelector("#calcButton")
const baseElem = document.querySelector("#base")
const heightElem = document.querySelector("#height")
const areaElem = document.querySelector("#area")
calcButton.addEventListener('click', () => {
    let base = Number(baseElem.value)
    let height = Number(heightElem.value)
    let area = base * height / 2
    areaElem.value = area
})