Simple implementation code of native js three-level linkage

//调用jsonp函数请求当前所在城市
jsonp('https://api.map.baidu.com/api?v=2.0&ak=Dv1NMU23dh1sGS9n2tUouDEYY96Dfzh3&s=1&callback=getCity');
window.onload=function(){
 //请求天气车数据
 btn.onclick=function (){
  jsonp(createUrl());
 }
};
function getCity(){
 function city(result){
  jsonp(createUrl(result.name));
 }
 var cityName = new BMap.LocalCity();
 cityName.get(city);
}
// 数据请求函数
function jsonp(url){
 var script = document.createElement('script');
 script.src = url;
 document.body.insertBefore(script, document.body.firstChild);
 document.body.removeChild(script);
}
//数据请求成功回调函数，用于将获取到的数据放入页面相应位置
function getWeather(response) {
 var oSpan = document.getElementsByClassName('info');
 var data = response.result.data;
 oSpan[0].innerHTML=data.realtime.city_name;
 oSpan[1].innerHTML=data.realtime.date;
 oSpan[2].innerHTML='星期'+data.weather[0].week;
 oSpan[3].innerHTML=data.realtime.weather.info;
 oSpan[4].innerHTML=data.realtime.weather.temperature+'℃';
 oSpan[5].innerHTML=data.realtime.wind.direct;
 oSpan[6].innerHTML=data.realtime.weather.humidity+'%';
 oSpan[7].innerHTML=data.realtime.time;
 oSpan[8].innerHTML=data.life.info.ziwaixian[0];
 oSpan[9].innerHTML=data.life.info.xiche[0];
 oSpan[10].innerHTML=data.life.info.kongtiao[0];
 oSpan[11].innerHTML=data.life.info.chuanyi[0];
 
 var aDiv = document.getElementsByClassName('future_box');
 for(var i=0; i<aDiv.length; i++){
  var aSpan = aDiv[i].getElementsByClassName(&#39;future_info&#39;);
  aSpan[0].innerHTML = data.weather[i].date;
  aSpan[1].innerHTML = &#39;星期&#39;+data.weather[i].week;
  aSpan[2].innerHTML =data.weather[i].info.day[1];
  aSpan[3].innerHTML = data.weather[i].info.day[2]+&#39;℃&#39;;
 }
 changeImg(response);
}
//根据获取到的数据更改页面中相应的图片
function changeImg(data){
 var firstImg = document.getElementsByTagName("img")[0];
 var firstWeatherId=data.result.data.realtime.weather.img;
 chooseImg(firstWeatherId,firstImg);
 
 var aImg = document.getElementById(&#39;future_container&#39;).getElementsByTagName(&#39;img&#39;);
 for(var j=0; j<aImg.length; j++){
  var weatherId = data.result.data.weather[j].info.day[0];
  chooseImg(weatherId,aImg[j]);
 }
}
//选择图片
function chooseImg(id,index){
 switch(id){
  case &#39;0&#39;:
   index.src=&#39;images/weather_icon/1.png&#39;;
   break;
  case &#39;1&#39;:
   index.src=&#39;images/weather_icon/2.png&#39;;
   break;
  case &#39;2&#39;:
   index.src=&#39;images/weather_icon/3.png&#39;;
   break;
  case &#39;3&#39;:
  case &#39;7&#39;:
  case &#39;8&#39;:
   index.src=&#39;images/weather_icon/4.png&#39;;
   break;
  case &#39;6&#39;:
   index.src=&#39;images/weather_icon/6.png&#39;;
   break;
  case &#39;13&#39;:
  case &#39;14&#39;:
  case &#39;15&#39;:
  case &#39;16&#39;:
   index.src=&#39;images/weather_icon/5.png&#39;;
   break;
  case &#39;33&#39;:
   index.src=&#39;images/weather_icon/7.png&#39;;
   break;
  default:
   index.src=&#39;images/weather_icon/8.png&#39;;
 }
}
//根据城市名创建请求数据及url
function createUrl(){
 var cityName = &#39;&#39;;
 if(arguments.length == 0) {
  cityName = document.getElementById(&#39;text&#39;).value;
 }else{
  cityName = arguments[0];
 }
 var url = &#39;https://op.juhe.cn/onebox/weather/query?cityname=&#39; + encodeURI(cityName) + &#39;&key=1053d001421b886dcecf81a38422a1a2&callback=getWeather&#39;;
 return url;
}