标签内元素在屏幕内非裁切，居中

var isW = function(){ return document.documentElement.clientWidth; }

var isH = function(){ return document.documentElement.clientHeight; }

var oVp = document.getElementById('viewport');

function css3(obj,attr,val){

var str = attr.charAt(0).toUpperCase() + attr.substring(1);

obj.style['Webkit'+str] = val;

obj.style['Moz'+str] = val;

obj.style['ms'+str] = val;

obj.style['O'+str] = val;

obj.style[attr] = val;

}

function setViewport(){

var gameS = oVp.offsetWidth/oVp.offsetHeight;

var screenS = isW()/isH();

if(gameS>screenS){

//高度拉伸

var _tc = isW()/oVp.offsetWidth;

css3(oVp,'transform','scale('+_tc+')');

}else{

//宽度拉伸

var _tc = isH()/oVp.offsetHeight;

css3(oVp,'transform','scale('+_tc+')');

}

}

//resize

function resizeSc(){

if(window.orientation){

window.addEventListener('orientationchange',function(){

setViewport();

},false);

}else{

window.addEventListener('resize',function(){

setViewport();

},false);

}

}

resizeSc();