function axios(method,url,data){
return new Promise((resolve, reject)=>{
const xhr = new XMLHttpRequest()
//打开一个 http请求并,传入方法和url
xhr.open(method,url)
console.log(xhr)
xhr.onreadystatechange = ()=>{
console.log(xhr.readyState)
if(xhr.readyState !== 4){
return
}
if(xhr.status === 200){
console.log('success')
resolve(xhr.response)
}else{
console.log('error')
reject(xhr.statusText)
}
}
xhr.send(data)
})
}
// const res = new axios('POST','www.baidu.com','hello baidu')