<!DOCTYPE html>
<html class="mobile">
<head>
<meta charset="UTF-8">
<title></title>
<style type="text/css">
.mobile #div1{
background: skyblue;
}
.pc #div1{
background: pink;
}
.pad #div1{
background: salmon;
}
.iphone #div1{
background: yellow;
}
.android #div1{
background: seagreen;
}
#div1{
height: 100px;
}
</style>
</head>
<body>
<div id="div1" >
</div>
<script type="text/javascript">
var html = document.querySelector('html')
function resize(){
var screneLength = window.innerWidth;
html.style.fontSize = window.innerWidth/7.5 + 'px'
if(screneLength>640&&screneLength<960){
html.className = 'pad'
}else if(screneLength>=960){
html.className = 'pc'
}else{
html.className = 'mobile'
}
if(navigator.userAgent.indexOf('Android')!==-1){
html.className = html.className + ' android'
}else if(navigator.userAgent.indexOf('iPhone')!==-1){
html.className = html.className + ' iphone'
}else if(navigator.userAgent.indexOf('iPad')!==-1){
html.className = html.className + ' ipad'
}
}
resize()
window.onresize = function(e){
resize()
}
</script>
</body>
</html>