lib/index.esm.js
function setStyle(el, key, val) {
  if (isObject(key)) {
    for (var k in key) {
      setStyle(el, k, key[k]);
    }
  } else {
    el.style[key] = val;
  }
}
function setStyle(el, key, val) {
  if (isObject(key)) {
    for (var k in key) {
      setStyle(el, k, key[k]);
    }
  } else {
    el.style[key] = val;
  }
}
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