js获取高度

//获取文档完整的高度

             function getScrollHeight() {

                 return Math.max(document.body.scrollHeight, document.documentElement.scrollHeight);

             }

         //获取当前可视范围高度

         function getClientHeight() {

             var clientheight = 0;

             if(document.body.clientHeight && document.documentElement.clientHeight) {

                 clientheight = Math.min(document.body.clientHeight, document.documentElement.clientHeight);

             } else {

                 clientheight = Math.max(document.body.clientHeight, document.documentElement.clientHeight);

             }

             return clientheight;

         }

         //获取滚动条的高度

         function getScrollTop() {

             var scrollTop = Math.max(document.documentElement.scrollTop, document.body.scrollTop);

             return scrollTop;

         }