html5 屏幕自适应代码

var standardDpi,dpi,w,scale;

w = window.screen.width;

if(w>0){

if(w < 320){

standardDpi = 120;

}else if(w < 480){

standardDpi = 160;

}else if(w < 640){

standardDpi = 240;

}else if(w < 960){

standardDpi = 320;

}else if(w < 1280){

standardDpi = 480;

}else{

standardDpi = 640;

}

}

dpi = 640*standardDpi/w;

dpi = Math.floor(dpi);

scale = 640/w;

document.querySelector("meta[name=viewport]").setAttribute('content','width=640,initial-scale=1.0, maximum-scale=3.0, minimum-scale=1.0,target-densitydpi='+dpi+', user-scalable=0');

if ("-ms-user-select" in document.documentElement.style && navigator.userAgent.match(/IEMobile\/10\.0/))

{

var msViewportStyle = document.createElement("style");

msViewportStyle.appendChild(

document.createTextNode("@-ms-viewport{width:auto!important}")

);

document.getElementsByTagName("head")[0].appendChild(msViewportStyle);

}