Number input with plus minus buttons

HTML

<div class="input-group">
  <input type="button" value="-" class="button-minus" data-field="quantity">
  <input type="number" step="1" max="" value="1" name="quantity" class="quantity-field">
  <input type="button" value="+" class="button-plus" data-field="quantity">
</div>

CSS

input,
textarea {
  border: 1px solid #eeeeee;
  box-sizing: border-box;
  margin: 0;
  outline: none;
  padding: 10px;
}

input[type="button"] {
  -webkit-appearance: button;
  cursor: pointer;
}

input::-webkit-outer-spin-button,
input::-webkit-inner-spin-button {
  -webkit-appearance: none;
}

.input-group {
  clear: both;
  margin: 15px 0;
  position: relative;
}

.input-group input[type='button'] {
  background-color: #eeeeee;
  min-width: 38px;
  width: auto;
  transition: all 300ms ease;
}

.input-group .button-minus,
.input-group .button-plus {
  font-weight: bold;
  height: 38px;
  padding: 0;
  width: 38px;
  position: relative;
}

.input-group .quantity-field {
  position: relative;
  height: 38px;
  left: -6px;
  text-align: center;
  width: 62px;
  display: inline-block;
  font-size: 13px;
  margin: 0 0 5px;
  resize: vertical;
}

.button-plus {
  left: -13px;
}

input[type="number"] {
  -moz-appearance: textfield;
  -webkit-appearance: none;
}

JavaScript

function incrementValue(e) {
  e.preventDefault();
  var fieldName = $(e.target).data('field');
  var parent = $(e.target).closest('div');
  var currentVal = parseInt(parent.find('input[name=' + fieldName + ']').val(), 10);

  if (!isNaN(currentVal)) {
    parent.find('input[name=' + fieldName + ']').val(currentVal + 1);
  } else {
    parent.find('input[name=' + fieldName + ']').val(0);
  }
}

function decrementValue(e) {
  e.preventDefault();
  var fieldName = $(e.target).data('field');
  var parent = $(e.target).closest('div');
  var currentVal = parseInt(parent.find('input[name=' + fieldName + ']').val(), 10);

  if (!isNaN(currentVal) && currentVal > 0) {
    parent.find('input[name=' + fieldName + ']').val(currentVal - 1);
  } else {
    parent.find('input[name=' + fieldName + ']').val(0);
  }
}

$('.input-group').on('click', '.button-plus', function(e) {
  incrementValue(e);
});

$('.input-group').on('click', '.button-minus', function(e) {
  decrementValue(e);
});