code: function (css, el) {
    var style = el.style
    if (isObject(css)) {
      var key
      for (key in css) {
        if (isDefine(style[cssjs(key)])) style[cssjs(key)] = css[key]
      }
    }
    if (isArray(css)) {
      var size = css.length
      var i
      for (i = 0; i < size; i++){
        if (isDefine(style[cssjs(css[i])])) style[cssjs(css[i])] = ""
      }
    }
  }
docs: (css →  object | array, el → dom)
  - add and remove style of element