es7学习教程之fetch解决异步嵌套问题的方法示例

function ajax(url){

   return new Promise(function(reslove,reject){
    let xmlHttp=new XMLHttpRequest();
    xmlHttp.open("get",url,true);
    xmlHttp.onreadystatechange=function(){
     if(xmlHttp.readyState==4&&xmlHttp.status==200){
      let data=JSON.parse(xmlHttp.responseText);
      reslove(data);
     }
    }
    xmlHttp.send(null);
   })
  }
  let uldom=document.getElementById("students");
  let url="http://192.168.0.57:8000/students.json";
  async function main(){
  let data=await ajax(url);
  
  let students=data;
  let html="";
  for(let i=0,l=students.length;i<l;i++){
   let name=students[i].name;
   let age=students[i].age;
   html+=`
   <li>姓名${name},年龄${age}</li>
   `
  }
  uldom.innerHTML=html;
  }
  main();

let uldom=document.getElementById("students");
  let url="http://192.168.0.57:8000/students.json";
  function main(){
   fetch(url).then(respone=>{
   return respone.json();
  }).then(data=>{
   let students=data;
   let html="";
   for(let i=0,l=students.length;i<l;i++){
    let name=students[i].name;
    let age=students[i].age;
    html+=`
    <li>姓名${name},年龄${age}</li>
    `
   }
   uldom.innerHTML=html;
  });
   
  }
  main();

let uldom=document.getElementById("students");
 let url="http://192.168.0.57:8000/students.json"; 
 async function main(){
  let respone = await fetch(url);
  let student = await respone.json();
  let html="";
  for (let i=0,l=students.length;i<l;i++){
   let name=students[i].name;
   let age=students[i].age;
   html+=`
   <li>姓名${name},年龄${age}</li>
   `
  }
  uldom.innerHTML=html;
  }
 main()