手写AJAXAJAX是Asynchronous JavaScript And XML的简称，它允许我们在不刷新整个页面的

AJAX是Asynchronous JavaScript And XML的简称，它允许我们在不刷新整个页面的情况下，就可以异步获取数据，并更新页面的部分内容。具体的实现步骤如下：

const ajax = (method,url,data,success,fail) => {
    const request =new XMLHTTPRequest()
    request.open = (method,url)
    request.onreadystatechange = function(){
        if(request.readyState === 4){
            if(request.status >= 200 && request.status < 300 || request.status === 304){
                success(request)
            }else{
                fail(request)
            }
        }
    }
    request.send()
}