code: function setStyle(el, key, val) {
    if (isObject(key)) {
      for (var k in key) {
        setStyle(el, k, key[k]);
      }
    } else {
      el.style[key] = val;
    }
  }
docs: 设置HTML元素样式值
  @param {HTMLElement} el 目标元素
  @param {String} key 样式key
  @param {String} val 样式值