获取css

function getStyle(elm,name){
    if(elm.style[name]){
        return elm.style[name]
    }else if(elm.currentStyle){
        return elm.currentStyle[name]
    }else if(document.defaultView&&document.defaultView.getComputedStyle){
        var name=name.replace(/([A-Z])/g,'-$1');
        name=name.toLowerCase();
        var s=document.defaultView.getComputedStyle(elm,'');
        return s&&s.getPropertyValue(name)
    }else{
        return null
    }
}