解决弹出框滚动穿透的问题（问题是body也会滚动）

参考 https://uedsky.com/2016-06/mobile-modal-scroll/ 感谢分享

案例页面：view-source:https://uedsky.com/demo/modal-scroll.html

第一步：给body加上个css类别样式

body.modal-open {
    position: fixed;
     100%;
}

第二部：创建核心函数：

/**
   * ModalHelper helpers resolve the modal scrolling issue on mobile devices
   * https://github.com/twbs/bootstrap/issues/15852
   * requires document.scrollingElement polyfill https://github.com/yangg/scrolling-element
   */
  var ModalHelper = (function(bodyCls) {
    var scrollTop;
    return {
    //打开弹窗
      afterOpen: function() {
        scrollTop = document.scrollingElement.scrollTop;
        document.body.classList.add(bodyCls);
        document.body.style.top = -scrollTop + 'px';
      },
     //关闭弹窗
      beforeClose: function() {
        document.body.classList.remove(bodyCls);
        // scrollTop lost after set position:fixed, restore it back.
        document.scrollingElement.scrollTop = scrollTop;
      }
    };
  })('modal-open');

　　第三部：打开/关闭弹窗，引用核心函数

//打开弹窗
$('.D_md12 .material .addbox').on('click',function(){

    		 $('.material_pop').addClass('show');
    		 ModalHelper.afterOpen();
	    });

//关闭弹窗
// pc点击空白区域关闭窗口
        $('.popbox:not(.publish_pop)').click(function(e){
          var _con = $('.popcontain');
          if(!_con.is(e.target) && _con.has(e.target).length === 0){
            $('.popbox').removeClass('show');
            ModalHelper.beforeClose();
          }
        });

//pc esc关闭窗口
        $(document).keyup(function(event){
            if(event.which=='27'){
                $('.popbox.show:not(.publish_pop)').removeClass('show');
                ModalHelper.beforeClose();
            }
        });

//PC 点击close按钮关闭弹窗
        $('.popbox:not(.publish_pop) .pop_closebtn').click(function(e){
            $('.popbox').removeClass('show');
            ModalHelper.beforeClose();
        });

备注：

document.scrollingElement

因为浏览器获取和设置 scrollTop 存在兼容性，为了简化上面的示例，我直接使用了 document.scrollingElement 这个新标准，对于不支持的浏览器我写了个 polyfill document.scrollingElement.js

检测函数：

<script>
(function() {
  function addScript(src, supported) {
   if(!supported)
     document.write('<script src="' + src + '" async ></' + 'script>');
  }
  addScript('../src/polyfills/document.scrollingElement.js', document.scrollingElement);
})();
</script>

document.scrollingElement.js

/**
 * polyfill for document.scrollingElement
 * https://github.com/yangg/scrolling-element
 */
(function () {
  if (document.scrollingElement) {
    return
  }
  var element = null
  function scrollingElement () {
    if (element) {
      return element
    } else if (document.body.scrollTop) {
      // speed up if scrollTop > 0
      return (element = document.body)
    }
    var iframe = document.createElement('iframe')
    iframe.style.height = '1px'
    document.documentElement.appendChild(iframe)
    var doc = iframe.contentWindow.document
    doc.write('<!DOCTYPE html><div style="height:9999em">x</div>')
    doc.close()
    var isCompliant = doc.documentElement.scrollHeight > doc.body.scrollHeight
    iframe.parentNode.removeChild(iframe)
    return (element = isCompliant ? document.documentElement : document.body)
  }
  Object.defineProperty(document, 'scrollingElement', {
    get: scrollingElement
  })
})()