Increase and descrease value via button click

index.html

<input type="number" id="number" value="0" />
<button type="button" onclick="increaseValue()">+</button>
<button type="button" onclick="decreaseValue()">-</button>
<button type="button" onclick="resetValue()">Reset</button>

script.js

function increaseValue() {
  var value = parseInt(document.getElementById('number').value, 10);
  value = isNaN(value) ? 0 : value;
  value++;
  document.getElementById('number').value = value;
}

function decreaseValue() {
  var value = parseInt(document.getElementById('number').value, 10);
  value = isNaN(value) ? 0 : value;
  value < 1 ? value = 1 : '';
  value--;
  document.getElementById('number').value = value;
}

function resetValue() {
  var value = 0;
  document.getElementById('number').value = value;
}