1.css，在public.index.css创建index.css

 html,
      body,
      #app {
        height: 100%;
        margin: 0px;
        padding: 0px;
      }
      .chromeframe {
        margin: 0.2em 0;
        background: #ccc;
        color: #4ea3fb;
        padding: 0.2em 0;
      }
      #loader-wrapper {
        position: fixed;
        top: 0;
        left: 0;
        width: 100%;
        height: 100%;
        z-index: 999999;
      }
      #loader {
        display: block;
        position: relative;
        left: 50%;
        top: 50%;
        width: 150px;
        height: 150px;
        margin: -75px 0 0 -75px;
        border-radius: 50%;
        border: 3px solid transparent;
        /* COLOR 1 */
        border-top-color: #4ea3fb;
        -webkit-animation: spin 2s linear infinite;
        /* Chrome, Opera 15+, Safari 5+ */
        -ms-animation: spin 2s linear infinite;
        /* Chrome, Opera 15+, Safari 5+ */
        -moz-animation: spin 2s linear infinite;
        /* Chrome, Opera 15+, Safari 5+ */
        -o-animation: spin 2s linear infinite;
        /* Chrome, Opera 15+, Safari 5+ */
        animation: spin 2s linear infinite;
        /* Chrome, Firefox 16+, IE 10+, Opera */
        z-index: 1001;
      }
      #loader:before {
        content: "";
        position: absolute;
        top: 5px;
        left: 5px;
        right: 5px;
        bottom: 5px;
        border-radius: 50%;
        border: 3px solid transparent;
        /* COLOR 2 */
        border-top-color: #4ea3fb;
        -webkit-animation: spin 3s linear infinite;
        /* Chrome, Opera 15+, Safari 5+ */
        -moz-animation: spin 3s linear infinite;
        /* Chrome, Opera 15+, Safari 5+ */
        -o-animation: spin 3s linear infinite;
        /* Chrome, Opera 15+, Safari 5+ */
        -ms-animation: spin 3s linear infinite;
        /* Chrome, Opera 15+, Safari 5+ */
        animation: spin 3s linear infinite;
        /* Chrome, Firefox 16+, IE 10+, Opera */
      }
      #loader:after {
        content: "";
        position: absolute;
        top: 15px;
        left: 15px;
        right: 15px;
        bottom: 15px;
        border-radius: 50%;
        border: 3px solid transparent;
        border-top-color: #4ea3fb;
        /* COLOR 3 */
        -moz-animation: spin 1.5s linear infinite;
        /* Chrome, Opera 15+, Safari 5+ */
        -o-animation: spin 1.5s linear infinite;
        /* Chrome, Opera 15+, Safari 5+ */
        -ms-animation: spin 1.5s linear infinite;
        /* Chrome, Opera 15+, Safari 5+ */
        -webkit-animation: spin 1.5s linear infinite;
        /* Chrome, Opera 15+, Safari 5+ */
        animation: spin 1.5s linear infinite;
        /* Chrome, Firefox 16+, IE 10+, Opera */
      }
      @-webkit-keyframes spin {
        0% {
          -webkit-transform: rotate(0deg);
          /* Chrome, Opera 15+, Safari 3.1+ */
          -ms-transform: rotate(0deg);
          /* IE 9 */
          transform: rotate(0deg);
          /* Firefox 16+, IE 10+, Opera */
        }
        100% {
          -webkit-transform: rotate(360deg);
          /* Chrome, Opera 15+, Safari 3.1+ */
          -ms-transform: rotate(360deg);
          /* IE 9 */
          transform: rotate(360deg);
          /* Firefox 16+, IE 10+, Opera */
        }
      }

      @keyframes spin {
        0% {
          -webkit-transform: rotate(0deg);
          /* Chrome, Opera 15+, Safari 3.1+ */
          -ms-transform: rotate(0deg);
          /* IE 9 */
          transform: rotate(0deg);
          /* Firefox 16+, IE 10+, Opera */
        }
        100% {
          -webkit-transform: rotate(360deg);
          /* Chrome, Opera 15+, Safari 3.1+ */
          -ms-transform: rotate(360deg);
          /* IE 9 */
          transform: rotate(360deg);
          /* Firefox 16+, IE 10+, Opera */
        }
      }
      #loader-wrapper .loader-section {
        position: fixed;
        top: 0;
        width: 51%;
        height: 100%;
        background: #fff;
        /* Old browsers */
        z-index: 1000;
        -webkit-transform: translateX(0);
        /* Chrome, Opera 15+, Safari 3.1+ */
        -ms-transform: translateX(0);
        /* IE 9 */
        transform: translateX(0);
        /* Firefox 16+, IE 10+, Opera */
      }

      #loader-wrapper .loader-section.section-left {
        left: 0;
      }

      #loader-wrapper .loader-section.section-right {
        right: 0;
      }

      /* Loaded */

      .loaded #loader-wrapper .loader-section.section-left {
        -webkit-transform: translateX(-100%);
        /* Chrome, Opera 15+, Safari 3.1+ */
        -ms-transform: translateX(-100%);
        /* IE 9 */
        transform: translateX(-100%);
        /* Firefox 16+, IE 10+, Opera */
        -webkit-transition: all 0.7s 0.3s cubic-bezier(0.645, 0.045, 0.355, 1.000);
        transition: all 0.7s 0.3s cubic-bezier(0.645, 0.045, 0.355, 1.000);
      }
      .loaded #loader-wrapper .loader-section.section-right {
        -webkit-transform: translateX(100%);
        /* Chrome, Opera 15+, Safari 3.1+ */
        -ms-transform: translateX(100%);
        /* IE 9 */
        transform: translateX(100%);
        /* Firefox 16+, IE 10+, Opera */
        -webkit-transition: all 0.7s 0.3s cubic-bezier(0.645, 0.045, 0.355, 1.000);
        transition: all 0.7s 0.3s cubic-bezier(0.645, 0.045, 0.355, 1.000);
      }

      .loaded #loader {
        opacity: 0;
        -webkit-transition: all 0.3s ease-out;
        transition: all 0.3s ease-out;
      }

      .loaded #loader-wrapper {
        visibility: hidden;
        -webkit-transform: translateY(-100%);
        /* Chrome, Opera 15+, Safari 3.1+ */
        -ms-transform: translateY(-100%);
        /* IE 9 */
        transform: translateY(-100%);
        /* Firefox 16+, IE 10+, Opera */
        -webkit-transition: all 0.3s 1s ease-out;
        transition: all 0.3s 1s ease-out;
      }

      /* JavaScript Turned Off */

      .no-js #loader-wrapper {
        display: none;
      }

      .no-js h1 {
        color: #222222;
      }
      #loader-wrapper .load_title {
        font-family: 'Open Sans';
        color: #4ea3fb;
        font-size: 36px;
        width: 100%;
        text-align: center;
        z-index: 9999999999999;
        position: absolute;
        top: 60%;
        opacity: 1;
        line-height: 30px;
      }

      #loader-wrapper .load_title p {
        height: 50px;
        padding-top: 10px;
        font-weight: normal;
        font-style: italic;
        font-size: 26px;
        color: #4ea3fb;
        opacity: 0.8;
      }

压缩版

html,body,#app{height:100%;margin:0;padding:0}.chromeframe{margin:.2em 0;background:#ccc;color:#4ea3fb;padding:.2em 0}#loader-wrapper{position:fixed;top:0;left:0;width:100%;height:100%;z-index:999999}#loader{display:block;position:relative;left:50%;top:50%;width:150px;height:150px;margin:-75px 0 0 -75px;border-radius:50%;border:3px solid transparent;border-top-color:#4ea3fb;-webkit-animation:spin 2s linear infinite;-ms-animation:spin 2s linear infinite;-moz-animation:spin 2s linear infinite;-o-animation:spin 2s linear infinite;animation:spin 2s linear infinite;z-index:1001}#loader:before{content:"";position:absolute;top:5px;left:5px;right:5px;bottom:5px;border-radius:50%;border:3px solid transparent;border-top-color:#4ea3fb;-webkit-animation:spin 3s linear infinite;-moz-animation:spin 3s linear infinite;-o-animation:spin 3s linear infinite;-ms-animation:spin 3s linear infinite;animation:spin 3s linear infinite}#loader:after{content:"";position:absolute;top:15px;left:15px;right:15px;bottom:15px;border-radius:50%;border:3px solid transparent;border-top-color:#4ea3fb;-moz-animation:spin 1.5s linear infinite;-o-animation:spin 1.5s linear infinite;-ms-animation:spin 1.5s linear infinite;-webkit-animation:spin 1.5s linear infinite;animation:spin 1.5s linear infinite}@-webkit-keyframes spin{0%{-webkit-transform:rotate(0deg);-ms-transform:rotate(0deg);transform:rotate(0deg)}100%{-webkit-transform:rotate(360deg);-ms-transform:rotate(360deg);transform:rotate(360deg)}}@keyframes spin{0%{-webkit-transform:rotate(0deg);-ms-transform:rotate(0deg);transform:rotate(0deg)}100%{-webkit-transform:rotate(360deg);-ms-transform:rotate(360deg);transform:rotate(360deg)}}#loader-wrapper .loader-section{position:fixed;top:0;width:51%;height:100%;background:#fff;z-index:1000;-webkit-transform:translateX(0);-ms-transform:translateX(0);transform:translateX(0)}#loader-wrapper .loader-section.section-left{left:0}#loader-wrapper .loader-section.section-right{right:0}.loaded #loader-wrapper .loader-section.section-left{-webkit-transform:translateX(-100%);-ms-transform:translateX(-100%);transform:translateX(-100%);-webkit-transition:all .7s .3s cubic-bezier(0.645,0.045,0.355,1.000);transition:all .7s .3s cubic-bezier(0.645,0.045,0.355,1.000)}.loaded #loader-wrapper .loader-section.section-right{-webkit-transform:translateX(100%);-ms-transform:translateX(100%);transform:translateX(100%);-webkit-transition:all .7s .3s cubic-bezier(0.645,0.045,0.355,1.000);transition:all .7s .3s cubic-bezier(0.645,0.045,0.355,1.000)}.loaded #loader{opacity:0;-webkit-transition:all .3s ease-out;transition:all .3s ease-out}.loaded #loader-wrapper{visibility:hidden;-webkit-transform:translateY(-100%);-ms-transform:translateY(-100%);transform:translateY(-100%);-webkit-transition:all .3s 1s ease-out;transition:all .3s 1s ease-out}.no-js #loader-wrapper{display:none}.no-js h1{color:#222}#loader-wrapper .load_title{font-family:'Open Sans';color:#4ea3fb;font-size:36px;width:100%;text-align:center;z-index:9999999999999;position:absolute;top:60%;opacity:1;line-height:30px}#loader-wrapper .load_title p{height:50px;padding-top:10px;font-weight:normal;font-style:italic;font-size:26px;color:#4ea3fb;opacity:.8}

2.html，在public.index.html里添加标签

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="utf-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <!-- <meta name="viewport" content="width=device-width,initial-scale=1.0"> -->
    <link rel="icon" href="<%= BASE_URL %>favicon.ico">
    <link rel="stylesheet" href="<%= BASE_URL %>font/iconfont.css">
    <title><%= htmlWebpackPlugin.options.title %></title>
    <link rel="stylesheet" href="./index.css">
  </head>
  <body>
    <noscript>
      <strong>We're sorry but <%= htmlWebpackPlugin.options.title %> doesn't work properly without JavaScript enabled. Please enable it to continue.</strong>
    </noscript>
    <div id="app">
      <div id="loader-wrapper">
        <div id="loader"></div>
        <div class="loader-section section-left"></div>
        <div class="loader-section section-right"></div>
        <div class="load_title">正在加载XXX系统,请耐心等待...
          <br>
          <p>v1.0</p>
        </div>
      </div>
    </div>
    <!-- built files will be auto injected -->
  </body>
</html>