更新一下：FormData确实很好用，不用刷新网页的情况下，可以直接完成我要的功能！

就是和warp搭配起来，有点麻烦。

            loadDom.onclick = function () {
                if (filesDom.value != "") {
                    var url = 'http://127.0.0.1:3030/';

                    var formData = new FormData();
                    loadedFile = filesDom.value;
                    formData.append("load", loadedFile);

                    var request = new XMLHttpRequest();
                    request.open("POST", url);

                    request.onload = function() {
                        if (request.readyState === request.DONE) {
                            if (request.status == 200) {
                                let response = request.responseText.split("\r\n");

                                let ew = JSON.parse( response[0] );
                                let yy = JSON.parse( response[1] );
                                for (var i = 0; i < ew.length; i++) {
                                    ewValue[i].value = ew[i];
                                    yyValue[i].value = yy[i];
                                }
                            }
                        }
                    };

                    request.send(formData);
                }
            }

rust做如下处理

#[tokio::main]
async fn main() {
    let default_reply2 = warp::path::end().and(warp::get()).map(|| Response::builder().body(default_reply()));

    let post_reply = warp::post()
        .and(warp::multipart::form())
        .and_then(post_reply);

    let routers = warp::get().and(default_reply2).or(post_reply);

    warp::serve(routers).run(([127, 0, 0, 1], 3030)).await;
}

async fn post_reply(form: warp::multipart::FormData) -> Result<impl warp::Reply, warp::Rejection> {
    let mut parts: Vec<warp::multipart::Part> = form
        .try_collect()
        .await
        .map_err(|_e| warp::reject::reject())?;
    
     if parts[0].name() == "save" {
        //....
     } else {
        //....
        let response_string = read_setting();
        Ok(Response::builder().body(response_string))  
     }
}