页面延迟加载

lazy.html

<style>
  .page{position:relative;-ms-flex-direction:column;flex-direction:column;min-height:100vh}
  .page-loading{background:center no-repeat;background-size:auto}
  .js-hidden{display:none!important}
</style>

<div id="page-loading" class="page page-loading" style="background-image:url(../../img/loading-0.gif)"></div>
<div id="app" class="page js-hidden">
</div>

<script type="text/javascript">
    window
        .addEventListener("load", function () {
            !function () {
                var e = document.getElementById("app");
                document.getElementById("page-loading")
                    .classList
                    .add("js-hidden"),
                    e.classList.remove("js-hidden")
            }()
        });
</script>