Edit in JSFiddle

var inputs = $('input[type="text"]');
var googleSubmitBtn = $('#google-submit');
var snackbar = $('#snackbar');

var inputName = $('#name');
var inputAge = $('#age');
var inputArea = $('#area');

function isLoading(status){
  if(status){
    $('html, body').addClass('wait');
    googleSubmitBtn.attr('disabled', true).html('입력중...');
  } else {
    $('html, body').removeClass('wait');
    googleSubmitBtn.attr('disabled', false).html('입력');
  }
}

function checkInput(){
  var isEmpty = false;
  $.each(inputs, function (index, element) {
    if (element.value === '') {
      alert('빈 칸이 있어요.');
      isEmpty = true;
      return false;
    }
  });
  return isEmpty;
}

$('#google-submit').click(function () {

  //빈값 체크
  if (checkInput()) { return; }

  // 입력중..
  isLoading(true);

  $.ajax({
    type: "GET",
    url: "https://script.google.com/macros/s/AKfycbwiHDc2dHHsppLBV9K6RuwWqqFAfkuqtRBMkcIOxo-ph6YP3PEw/exec",
    data: {
      "이름": inputName.val(),
      "나이": inputAge.val(),
      "사는곳": inputArea.val()
    },
    success: function (response) {
      isLoading(false);

      snackbar.html('입력이 완료됐습니다.').addClass('show');
      setTimeout(function () {
        snackbar.removeClass('show');
      }, 3000);

      //값 비워주기
      inputName.val('');
      inputAge.val('');
      inputArea.val('');
    },
    error: function (request, status, error) {
      isLoading(false);
      console.log("code:" + request.status + "\n" + "error:" + error);
      console.log(request.responseText);
    }
  });
});

<div>
  <label for="name">이름</label>
  <input type="text" id="name" name="name">
</div>
<div>
  <label for="age">나이</label>
  <input type="number" id="age" name="age" min="1">
</div>
<div>
  <label for="area">사는곳</label>
  <input type="text" id="area" name="area">
</div>
<div>
  <button id="google-submit">입력</button>
</div>

<div id="snackbar"></div>

html.wait *,
html.wait,
body.wait *,
body.wait {
  cursor: progress !important;
}

#snackbar {
  visibility: hidden;
  min-width: 250px;
  margin-left: -125px;
  background-color: #333;
  color: #fff;
  text-align: center;
  border-radius: 2px;
  padding: 16px;
  position: fixed;
  z-index: 1;
  left: 50%;
  bottom: 30px;
  font-size: 17px;
}

#snackbar.show {
  visibility: visible;
  -webkit-animation: fadein 0.5s, fadeout 0.5s 2.5s;
  animation: fadein 0.5s, fadeout 0.5s 2.5s;
}

@-webkit-keyframes fadein {
  from {
    bottom: 0;
    opacity: 0;
  }

  to {
    bottom: 30px;
    opacity: 1;
  }
}

@keyframes fadein {
  from {
    bottom: 0;
    opacity: 0;
  }

  to {
    bottom: 30px;
    opacity: 1;
  }
}

@-webkit-keyframes fadeout {
  from {
    bottom: 30px;
    opacity: 1;
  }

  to {
    bottom: 0;
    opacity: 0;
  }
}

@keyframes fadeout {
  from {
    bottom: 30px;
    opacity: 1;
  }

  to {
    bottom: 0;
    opacity: 0;
  }
}