code: function getOffset(el, param) {
      var el, l,  r, b, t;
      if (!el) {
        return;
      }
      if (!param) {
        param = {x: 0, y: 0};
      }
  
      if (el != window) {
        el = el.getBoundingClientRect();
        l = el.left;
        t = el.top;
        r = el.right;
        b = el.bottom;
      } else {
        l = 0;
        t = 0;
        r = l + el.innerWidth;
        b = t + el.innerHeight;
      }
      return {
        'left': l,
        'top': t,
        'right': r + param.x,
        'bottom': b + param.y
      };
    }
docs: [getOffset 获取边距尺寸]
  @param  {[type]} el   [description]
  @param  {[type]} param [description]
  @return {[type]}       [description]