var xhr = new XMLHttpRequest();
xhr.open('GET', url/file,true);
xhr.Onreadystatechange= function() {
 if(xhr.readyState==4){
  if(xhr.status==200){
   var data=xhr.responseText;
    console.log(data);
 }
};
xhr.Onerror= function() {
 console.log("Oh, error");
};
xhr.send();

fetch(url).then(respOnse=> response.json())//解析为可读数据
 .then(data => console.log(data))//执行结果是 resolve就调用then方法
 .catch(err => console.log("Oh, error", err))//执行结果是 reject就调用catch方法

//HTML部分
 

 
Fetch Api sandbox
 请求本地文本数据
 请求本地json数据
 请求网络接口
 


 

 
 

document.getElementById('button1').addEventListener('click',getText);
function getText(){
 fetch("test.txt")
  .then((res) => res.text())//注意：此处是res.text()
  .then(data => {
  console.log(data);
  document.getElementById('output').innerHTML = data;
  })
  .catch(err => console.log(err));
}

document.getElementById('button2').addEventListener('click',getJson);
function getJson(){
 fetch("posts.json")
  .then((res) => res.json())
  .then(data => {
  console.log(data);
  let output = '';
  data.forEach((post) => {
   output += `
${post.title}
`;
  })
  document.getElementById('output').innerHTML = output;
  })
  .catch(err => console.log(err));
}

document.getElementById('button3').addEventListener('click',getExternal);
function getExternal(){
 // https://api.github.com/users
 fetch("https://api.github.com/users")
  .then((res) => res.json())
  .then(data => {
  console.log(data);
  let output = '';
  data.forEach((user) => {
   output += `
${user.login}
`;
  })
  document.getElementById('output').innerHTML = output;
  })
  .catch(err => console.log(err));
}