#div1 {
  width: 200px;
  height: 200px;
  background: red;
}

var oDiv = document.getElementById('div1'); 
oDiv.currentStyle.width;
Chrome/FF获取非行间样式
var oDiv = document.getElementById('div1');
oDiv.getComputedStyle(oDiv,false).width;

var oDiv = document.getElementById('div1');
var eleWidth = oDiv.currentStyle && oDiv.currentStyle.width || getComputedStyle(oDiv,false).width;

function getStyle(obj,name){
  return obj.currentStyle?obj.currentStyle[name]:getComputedStyle(obj,false)[name];
}