js 动态添加class封装(es6语法)

export function hasClass(el, className) {
  let reg = new RegExp(\'(^|\\s)\' + className + \'(\\s|$)\')
  return reg.test(el.className)
}

export function addClass(el, className) {
  if (hasClass(el, className)) {
    return
  }

  let newClass = el.className.split(\' \')
  newClass.push(className)
  el.className = newClass.join(\' \')
}

addClass(元素, \'item-类名\')