错误:发送后设置标头-帮助我了解原因? [英] Error: Setting header after it is sent - Help me understand why?
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问题描述
我不知道将标头发送给客户端后如何设置标头吗?
代码:在表单提交过程中，发出了ajax请求，响应是一个返回给客户端的json对象.
code: During form submission a post ajax request is made, the response is a json object that is returned to the client.
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?
I am commented out most of the code to find out why, at this point I am only doing one res.json() after a post request is made. I don't understand at what point I am RE-SETTING the header/ or returning a reponse twice?
但我收到此错误:
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)
index.js
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;
}
}
myscript.js ---前端客户端
myscript.js --- front end client side client
document.getElementById("createNewList").addEventListener('submit', function(e) {
e.preventDefault();
// serialize form to convert into JSOn object
let form_data = formSerialize(document.getElementById("createNewList"));
// AJAX fetch()
fetch('/', {
method: 'POST',
headers: {
"Content-Type": "application/json; charset=utf-8",
// "Content-Type": "application/x-www-form-urlencoded",
},
body: form_data
})
.then(function(response) {
if(response.ok)
return response.json();
})
.then(function(user_json) {
console.log(user_json);
console.log(user_json);
create_todays_todo_list(user_json);
});
});
// add event listener of the to do list i.e. adding tasks deleting tasks, completed tasks
// document.getElementById("toDoList_form").addEventListener('submit', function(e) {
// e.preventDefault();
// console.log("clikeddddddddd");
// // AJAX send added task to server
// let list_item = document.getElementById("list_item").innerHTML;
// let user = document.getElementById("user_name_heading").innerHTML;
// let data = {"user": user, "list_item": list_item}
// console.log(data);
// AJAX fetch()
// fetch('/', {
// method: 'POST',
// headers: {
// "Content-Type": "application/json; charset=utf-8",
// // "Content-Type": "application/x-www-form-urlencoded",
// },
// body: data
// })
// .then(function(response) {
// if(response.ok)
// return response.json();
// })
// .then(function(retrievedItemsFromServer) {
// console.log(retrievedItemsFromServer);
// });
//
// });
/// functionssss
// serialize form function
function formSerialize(form) {
var input = form.getElementsByTagName("input");
var formData = {};
for (var i = 0; i < input.length; i++) {
formData[input[i].name] = input[i].value;
}
return formData = JSON.stringify(formData);
}
function create_todays_todo_list(user_json) {
// 1. hide the create list form form
document.getElementById("createNewList").style.display="none";
// 2. display the to do list div
document.getElementById("toDoList").style.display="flex";
// 3. display the user's name and date as logged in on the page
document.getElementById("user_name_heading").innerHTML = user_json.userName;
document.getElementById("user_date_signup_heading").innerHTML = user_json.userDate;
}
推荐答案
console.log(body.req); 这是错误的.它应该是 console.log(req.body); .通常在程序退出但堆栈中仍然存在函数回调时会发生这种情况.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)
console.log(body.req); this is wrong. It should be console.log(req.body);. This generally happens when the program exited but still, there is a function callback in the stack. This should fix your problem. If it didn't please share the console log if printed any
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