将子div边缘滚动到父div边缘

Question

水平滚动很好。但是我希望在滚动时，每个子div的边缘都会卡在父div的边缘。因此，子div可见正确，不会被隐藏，这是任何部分。请看下面的代码。

jQuery(function($) {
  $.fn.hScroll = function(amount) {
    amount = amount || 50;
    $(this).bind("DOMMouseScroll mousewheel", function(event) {
      var oEvent = event.originalEvent,
        direction = oEvent.detail ? oEvent.detail * -amount : oEvent.wheelDelta,
        position = $(this).scrollLeft();
      position += direction > 0 ? -amount : amount;
      $(this).scrollLeft(position);
      event.preventDefault();
    })
  };
});

$(document).ready(function() {
  $('#box').hScroll(50); // You can pass (optionally) scrolling amount
});

body {
  margin: 0;
  padding: 0;
}

.container {
  display: flex;
}

#box-left {
  min-width: 50%;
  height: 100vh;
  background: #E6E6E6;
}

#box {
  display: flex;
  display: -webkit-flex;
  width: 50vw;
  height: 100vh;
  align-items: center;
  overflow-x: hidden;
}

.item {
  display: table-cell;
  min-width: 50vw;
  height: 100vh;
  font-size: 140px;
  text-align: center;
}

.item:nth-child(odd) {
  background: #1D5D95;
}

.item:nth-child(even) {
  background: #CCCCCC;
}

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<div class="container">
  <div id="box-left">left box</div>
  <div id="box">
    <div class="item">1</div>
    <div class="item">2</div>
    <div class="item">3</div>
    <div class="item">4</div>
    <div class="item">5</div>
    <div class="item">6</div>
    <div class="item">7</div>
    <div class="item">8</div>
    <div class="item">9</div>
  </div>
</div>