我不知道将标头发送给客户端后如何设置标头？
代码：：在表单提交过程中，发出了ajax请求，响应是返回给客户端的json对象。
我被注释掉了大部分代码，以找出原因，目前，我仅在发出发布请求后才执行一个res.json（）。我不知道在什么时候我要重新设置标题/或两次返回响应？
但我收到此错误：
#include <stdio.h> #include <stdlib.h> #include <alsa/asoundlib.h> main (int argc, char *argv[]) { int i; int err; char *buffer; int buffer_frames = 128; unsigned int rate = 44100; snd_pcm_t *capture_handle; snd_pcm_hw_params_t *hw_params; snd_pcm_format_t format = SND_PCM_FORMAT_FLOAT; // snd_pcm_format_t format = SND_PCM_FORMAT_S16_LE; if ((err = snd_pcm_open (&capture_handle, argv[1], SND_PCM_STREAM_CAPTURE, 0)) < 0) { fprintf (stderr, "cannot open audio device %s (%s)\n", argv[1], snd_strerror (err)); exit (1); } fprintf(stdout, "audio interface opened\n"); if ((err = snd_pcm_hw_params_malloc (&hw_params)) < 0) { fprintf (stderr, "cannot allocate hardware parameter structure (%s)\n", snd_strerror (err)); exit (1); } fprintf(stdout, "hw_params allocated\n"); if ((err = snd_pcm_hw_params_any (capture_handle, hw_params)) < 0) { fprintf (stderr, "cannot initialize hardware parameter structure (%s)\n", snd_strerror (err)); exit (1); } fprintf(stdout, "hw_params initialized\n"); if ((err = snd_pcm_hw_params_set_access (capture_handle, hw_params, SND_PCM_ACCESS_RW_INTERLEAVED)) < 0) { fprintf (stderr, "cannot set access type (%s)\n", snd_strerror (err)); exit (1); } fprintf(stdout, "hw_params access setted\n"); if ((err = snd_pcm_hw_params_set_format (capture_handle, hw_params, format)) < 0) { fprintf (stderr, "cannot set sample format (%s)\n", snd_strerror (err)); exit (1); } fprintf(stdout, "hw_params format setted\n"); if ((err = snd_pcm_hw_params_set_rate_near (capture_handle, hw_params, &rate, 0)) < 0) { fprintf (stderr, "cannot set sample rate (%s)\n", snd_strerror (err)); exit (1); } fprintf(stdout, "hw_params rate setted\n"); if ((err = snd_pcm_hw_params_set_channels (capture_handle, hw_params, 2)) < 0) { fprintf (stderr, "cannot set channel count (%s)\n", snd_strerror (err)); exit (1); } fprintf(stdout, "hw_params channels setted\n"); if ((err = snd_pcm_hw_params (capture_handle, hw_params)) < 0) { fprintf (stderr, "cannot set parameters (%s)\n", snd_strerror (err)); exit (1); } fprintf(stdout, "hw_params setted\n"); snd_pcm_hw_params_free (hw_params); fprintf(stdout, "hw_params freed\n"); if ((err = snd_pcm_prepare (capture_handle)) < 0) { fprintf (stderr, "cannot prepare audio interface for use (%s)\n", snd_strerror (err)); exit (1); } fprintf(stdout, "audio interface prepared\n"); buffer = malloc(128 * snd_pcm_format_width(format) / 8 * 2); fprintf(stdout, "buffer allocated\n"); FILE *fp = fopen("in.pcm", "a+"); //for (i = 0; i < 10; ++i) { i = 0; while(++i) { snd_pcm_wait(capture_handle, 1000); if ((err = snd_pcm_readi (capture_handle, buffer, buffer_frames)) != buffer_frames) { fprintf (stderr, "read from audio interface failed (%s)\n", snd_strerror (err)); exit (1); } fwrite(buffer, 1, buffer_frames, fp); fprintf(stdout, "read %d done\n", i); } fclose(fp); free(buffer); fprintf(stdout, "buffer freed\n"); snd_pcm_close (capture_handle); fprintf(stdout, "audio interface closed\n"); exit (0); }
index.js
Error [ERR_HTTP_HEADERS_SENT]: Cannot set headers after they are sent to the client
at ServerResponse.setHeader (_http_outgoing.js:470:11)
at ServerResponse.header (/home/shahyan/Videos/FrontendProject-masters/notes-js/beginner/js-fundamentals-functional/todoApp/node_modules/express/lib/response.js:767:10)
at ServerResponse.send (/home/shahyan/Videos/FrontendProject-masters/notes-js/beginner/js-fundamentals-functional/todoApp/node_modules/express/lib/response.js:170:12)
at done (/home/shahyan/Videos/FrontendProject-masters/notes-js/beginner/js-fundamentals-functional/todoApp/node_modules/express/lib/response.js:1004:10)
at Object.exports.renderFile (/home/shahyan/Videos/FrontendProject-masters/notes-js/beginner/js-fundamentals-functional/todoApp/node_modules/pug/lib/index.js:412:12)
at View.exports.__express [as engine] (/home/shahyan/Videos/FrontendProject-masters/notes-js/beginner/js-fundamentals-functional/todoApp/node_modules/pug/lib/index.js:455:11)
at View.render (/home/shahyan/Videos/FrontendProject-masters/notes-js/beginner/js-fundamentals-functional/todoApp/node_modules/express/lib/view.js:135:8)
at tryRender (/home/shahyan/Videos/FrontendProject-masters/notes-js/beginner/js-fundamentals-functional/todoApp/node_modules/express/lib/application.js:640:10)
at Function.render (/home/shahyan/Videos/FrontendProject-masters/notes-js/beginner/js-fundamentals-functional/todoApp/node_modules/express/lib/application.js:592:3)
at ServerResponse.render (/home/shahyan/Videos/FrontendProject-masters/notes-js/beginner/js-fundamentals-functional/todoApp/node_modules/express/lib/response.js:1008:7)
myscript.js ---前端客户端
var express = require('express');
var router = express.Router();
let users = [];
/* GET home page. */
router.get('/', function(req, res, next) {
res.render('index', { title: 'Express' });
});
router.post('/', function(req, res, next) {
// check post valued are true
if(req.body.fname && req.body.list_name && req.body.list_date) {
// try {
addNewUser(req.body);
res.json({
"message":"Successfully signed up!",
"userName": req.body.fname,
"userDate": req.body.list_date
});
// } catch(e){
// signup failed
// res.json(res.status(status).json(obj), "Sign up failed...");
// }
}
// if(req.body.list_item) {
// console.log(req.body.list_item);
// }
console.log(body.req);
});
module.exports = router;
function addNewUser(data) {
try {
users.push(
{
"fname":data.fname,
"list_name": data.list_name,
"list_date": data.list_date
}
);
} catch(e) {
console.log("Failed to add user ", e);
throw e;
}
}
答案 0 :(得分：0)
console.log(body.req);，这是错误的。它应该是console.log(req.body);。通常会在程序退出时发生，但堆栈中仍然存在函数回调。这应该可以解决您的问题。如果没有，请共享控制台日志（如果有的话）