SOURCE

function jsonp({url,params,callback=null}){
  return new Promise(function(resolve,reject){
    let script = document.createElement('script');
    let tempUrl = new URLSearchParams({...params,callback}).toString()
    script.src = url+'?'+tempUrl;
    document.body.appendChild(script)
    window[callback] = function(data){
      resolve(data);
      document.body.removeChild(script);
    }
  })
}
// jsonp({
//   url:"https://mock.yonyoucloud.com/mock/316/billcode/billcode/billcode/loggleCodeRuleById",
//   params:{
//     pkBillCodeBase:11,
//     bool:true,
//   }
// }).then( res =>{
//   console.log(res)
// })

let xhr = new XMLHttpRequest()
// xhr.timeout = 20;//设置超时时间
xhr.withCredentials = true;//设置是否携带凭证
// xhr.UNSENT 0,xhr.DONE 4
xhr.onreadystatechange = function(){
  console.log(xhr.readyState,'√')
   if(xhr.readyState == 4){
     console.log(xhr.getResponseHeader('Content-Type'))
     console.log('responseType',xhr.responseText)
   }
  if(xhr.readyState == 4 && xhr.status == 200){
    console.log('success',xhr.response)
  }
}
xhr.onerror = function(e){
  console.log('error')
}
// xhr.upload.addEventListner('progress',callback,false)
//open方法用来初始化一个请求
xhr.open('GET','http://localhost:4000/test1',true)
xhr.setRequestHeader("Content-Type", "application/json" );
// xhr.setRequestHeader('Accept','*/*');
// xhr.setRequestHeader("Access-Control-Allow-Origin", "*" );
xhr.overrideMimeType('text/plain; charset = utf-8');
xhr.send()
// xhr.abort();//终止xhr请求