<body class="body_bj"> </body> <script> var h = document.body.clientHeight; console.log(h); realh = h - 50; $(".body_bj").css("background-size","100%"+realh+"px"); </script>
var w=window.innerWidth || document.documentElement.clientWidth || document.body.clientWidth; var h=window.innerHeight || document.documentElement.clientHeight || document.body.clientHeight;