使用原生JS发送AJAX请求（XML，JSON解析）

mybutton.addEventListener('click', (e) => {
    let request = new XMLHttpRequest()
    request.onreadystatechange = () => {
        if(request.readyState === 4) {
            console.log('请求完毕')
            if(request.status >= 200 & request.status <= 300) {
                console.log('请求成功')
                console.log(request.responseText)
                //解析xml
                //let parser = new DOMParser();
                //let xmlDoc = parser.parseFromString(request.responseText, "text/xml")
                //let body=xmlDoc.getElementsByTagName('body')[0].textContent
                //console.log(body)
                //解析json    服务器返回的是字符串            
                let string = request.responseText
                let obj = window.JSON.parse(string)
                console.log(obj)
                console.log(obj.note)
                console.log(obj.note.to)
            } else if(request.status >= 400) {
                console.log('请求失败')
            }
        }
    }
    request.open('GET', '/xxx')
    request.send()
})