js获取动态加载图片大小

var img=new Image();


img.onreadystatechange=function(){
    if(img&&img.readyState&&img.readyState=='complete'){
       alert(img.width);
    }
}
img.src = url;


    //....
/*
var img = new Image();
img.onload = function(){
 var width = img.width;
 var height = img.height;
alert(width);
}
img.src = url;
*/