数据:
const data= { "B":[{"cityName":"北京","code":"110100"}], "S":[{"cityName":"上海","code":"310100"},{"cityName":"深圳","code":"440300"}], "C":[{"cityName":"成都","code":"510100"}], "F":[{"cityName":"佛山","code":"440600"}], "W":[{"cityName":"无锡","code":"320200"}], "N":[{"cityName":"南京","code":"320600"}] }
获取key 并按字母顺序排列
getCityLetter(data) {
return Object.keys(data).sort();
}