JS添加class类名

function toggleClass (ele, className) {
  if (!ele || !className) {
    return
  }
  let classString = ele.className
  const nameIndex = classString.indexOf(className)
  if (nameIndex === -1) {
    classString += ' ' + className
  } else {
    classString =
      classString.substr(0, nameIndex) +
      classString.substr(nameIndex + className.length)
  }
  ele.className = classString
}

// toggleClass(document.body, 'custom-theme')
// 再次添加相同类名即为删除