如何将 json 响应映射到 javascript 中的 UI

这是您可以使用的一些代码：

    <script>
    let use_api = function(){
        req = new XMLHttpRequest()
        req.setRequestHeader("Content-type", "application/json");
        req.onreadystatechange = function(){
            if(req.readyState == 4 && req.status==200){
               let data = JSON.parse(xhr.responseText);
               //here you should update your UI with the received data!  
            }
        }
        let req_body = JSON.stringfy({"username":"asdfasdf"}) //username is just an example, you should write things you want to send to API endpoint
        req.open('POST',url,true)
        req.send(req_body)

    }
</script>

也看看这个。
祝你好运。