how do i get input values inputted into input field 'in real-time' and use the input values?

tipButtons.forEach(tipButton => {
    tipButton.addEventListener('click', (e) => {

if(e.target.value === "") {
            console.log('custom')

            tipAmount.innerHTML = `$${((billAmount * customTip) / numberOfPeople).toFixed(2)}`;
            totalAmount.innerHTML = `$${(billPerPerson + ((billAmount * customTip) / numberOfPeople)).toFixed(2)}`;
        }