[英]How to fix “Error: Can't set headers after they are sent” in Express
I have recently been developing a MERN application and I have recently came into the trouble that express is saying that I am setting headers after they are sent. 我最近正在开发MERN应用程序,最近遇到了麻烦,快递表示我要在发送头之后设置头。
I am using mongo db and trying to update a user profile. 我正在使用mongo db并尝试更新用户配置文件。
I have tried to comment out my res.send points to find the issue but I have failed to do so. 我试图注释掉我的res.send发送点以找到问题,但我没有这样做。
Here is my post method for updating the user profile: 这是我更新用户个人资料的发布方法:
app.post("/api/account/update", (req, res) => {
const { body } = req;
// Validating and Checking Email
if (body.email) {
var email = body.email;
email = email.toLowerCase();
email = email.trim();
body.email = email;
User.find(
{
email: body.email
},
(err, previousUsers) => {
if (previousUsers.length > 0) {
return res.send({
success: false,
message:
"Error: There is already another account with that email address"
});
} else {
}
}
);
}
// Validating Names Function
function checkName(name) {
var alphaExp = /^[a-zA-Z]+$/;
if (!name.match(alphaExp)) {
return res.send({
success: false,
message: "Error: Names cannot contain special characters or numbers"
});
}
}
checkName(body.firstName);
checkName(body.lastName);
// Making sure that all fields cannot be empty
if (!body.email && !body.firstName && !body.lastName) {
return res.send({
success: false,
message: "Error: You cannot submit nothing"
});
}
// Getting User ID from the current session
UserSession.findById(body.tokenID, function(err, userData) {
// Finding User ID using the current users session token
if (userData.isDeleted) {
return res.send({
success: false,
message:
"Error: Session token is no longer valid, please login to recieve a new one"
});
}
// Deleting the token ID from the body object as user table entry doesnt store tokens
delete body.tokenID;
// Finding the user profile and updating fields that are present
User.findByIdAndUpdate(userData.userId, body, function(err, userInfo) {
if (!err) {
return res.send({
success: true,
message: "Success: User was updated successfully"
});
}
});
});
});
This is the call that I am doing to the backend of the site: 这是我对网站后端的呼叫:
onUpdateProfile: function(fieldsObj) {
return new Promise(function(resolve, reject) {
// Get Session Token
const obj = getFromStorage("the_main_app");
// Defining what fields are getting updated
fieldsObj.tokenID = obj.token;
// Post request to backend
fetch("/api/account/update", {
method: "POST",
headers: {
"Content-Type": "application/json"
},
body: JSON.stringify(fieldsObj)
})
.then(res => {
console.log("Verify Token - Res");
return res.json();
})
.then(json => {
console.log("Verify Token JSON", json);
if (json.success) {
window.location.href = `/manage-account?success=${json.success}`;
} else {
window.location.href = `/manage-account?success=${json.success}`;
}
});
});
}
Here is my error message that I am getting: 这是我收到的错误消息:
Error: Can't set headers after they are sent.
at validateHeader (_http_outgoing.js:491:11)
at ServerResponse.setHeader (_http_outgoing.js:498:3)
at ServerResponse.header (C:\Users\kieran.corkin\Desktop\Projects\Mern Template Final\mern-cra-and-server\server\node_modules\express\lib\response.js:767:10)
at ServerResponse.send (C:\Users\kieran.corkin\Desktop\Projects\Mern Template Final\mern-cra-and-server\server\node_modules\express\lib\response.js:170:12)
at ServerResponse.json (C:\Users\kieran.corkin\Desktop\Projects\Mern Template Final\mern-cra-and-server\server\node_modules\express\lib\response.js:267:15)
at ServerResponse.send (C:\Users\kieran.corkin\Desktop\Projects\Mern Template Final\mern-cra-and-server\server\node_modules\express\lib\response.js:158:21)
at C:\Users\kieran.corkin\Desktop\Projects\Mern Template Final\mern-cra-and-server\server\routes\api\account.js:270:22
at C:\Users\kieran.corkin\Desktop\Projects\Mern Template Final\mern-cra-and-server\server\node_modules\mongoose\lib\model.js:4641:16
at process.nextTick (C:\Users\kieran.corkin\Desktop\Projects\Mern Template Final\mern-cra-and-server\server\node_modules\mongoose\lib\query.js:2624:28)
at _combinedTickCallback (internal/process/next_tick.js:131:7)
at process._tickCallback (internal/process/next_tick.js:180:9)
[nodemon] app crashed - waiting for file changes before starting...
Can anyone help me with this? 谁能帮我这个?
EDIT 编辑
I have changed my code, this seems to now work however I feel like its a little messy when put together. 我已经更改了代码,现在似乎可以了,但是放在一起时感觉有点混乱。 Any refactoring tips?
有重构提示吗?
Code: 码:
app.post("/api/account/update", (req, res) => {
// Preform checks on data that is passed through
const { body } = req;
var messages = {
ExistedUser:
"Error: There is already another account with that email address",
NameFormat: "Error: Names cannot contain special characters or numbers",
BlankInputs: "Error: You cannot submit nothing",
accountLoggedOut:
"Error: Session token is no longer valid, please login to recieve a new one",
successfullyUpdated: "Success: User was updated successfully"
};
var usersFound;
if (body.email) {
var email = body.email;
email = email.toLowerCase();
email = email.trim();
body.email = email;
User.find(
{
email: body.email
},
(err, UserCount) => {
usersFound = UserCount;
}
);
}
function capitalize(text) {
return text.replace(/\b\w/g, function(m) {
return m.toUpperCase();
});
}
if (body.firstName) {
body.firstName = capitalize(body.firstName);
}
if (body.lastName) {
body.lastName = capitalize(body.lastName);
}
//Making sure that all fields cannot be empty
if (!body.email && !body.firstName && !body.lastName) {
return res.send({
success: false,
message: messages.BlankInputs
});
}
// Getting User ID from the current session
UserSession.findById(body.tokenID, function(err, userData) {
// Finding User ID using the current users session token
if (userData.isDeleted) {
return res.end({
success: false,
message: messages.accountLoggedOut
});
}
if (userData) {
// Deleting the token ID from the body object as user table entry doesnt store tokens
delete body.tokenID;
// Finding the user profile and updating fields that are present
User.findByIdAndUpdate(userData.userId, body, function(err, userInfo) {
if (userInfo) {
if (!usersFound.length > 0) {
return res.send({
success: true,
message: messages.successfullyUpdated
});
} else {
return res.send({
success: false,
message: messages.ExistedUser
});
}
}
});
}
});
});
You're calling res.send()
twice. 您两次调用
res.send()
。 res.send()
ends the process. res.send()
结束该过程。 You ought to refactor such that you call res.write()
and only call res.send()
when you're done. 您应该进行重构,以便在完成后调用
res.write()
并仅调用res.send()
。
This StackOverflow link describes the difference in more detail. 该StackOverflow链接更详细地描述了差异。 What is the difference between res.send and res.write in express?
express中的res.send和res.write有什么区别?
I believe this is happening, as you're trying to send a response after the first / initial response has already been sent to the browser. 我相信这种情况正在发生,因为您正在尝试在第一个/初始响应已发送到浏览器之后发送响应。 For example:
例如:
checkName(body.firstName);
checkName(body.lastName);
Running this function twice is going to try and yield 2 different "response" messages. 两次运行此功能将尝试产生2个不同的“响应”消息。
The product of a single route, should ultimately be a single response. 单一途径的产物最终应该是单一反应。
Thanks for all your help on this issue. 感谢您在此问题上的所有帮助。
Here is my final code that allowed it to work. 这是我允许其工作的最终代码。
I have also tried to "refactor" it too. 我也尝试过“重构”它。 Let me know if you'd do something else.
让我知道您是否还要做其他事情。
app.post("/api/account/update", (req, res) => {
const { body } = req;
console.log(body, "Logged body");
// Defining objects to be used at the end of request
var updateUserInfo = {
userInfo: {},
sessionToken: body.tokenID
};
var hasErrors = {
errors: {}
};
// Checking that there is at least one value to update
if (!body.email && !body.firstName && !body.lastName) {
var blankError = {
success: false,
message: "Error: You cannot change your details to nothing"
};
hasErrors.errors = { ...hasErrors.errors, ...blankError };
} else {
console.log("Normal Body", body);
clean(body);
console.log("Cleaned Body", body);
updateUserInfo.userInfo = body;
delete updateUserInfo.userInfo.tokenID;
}
// Function to check if object is empty
function isEmpty(obj) {
if (Object.keys(obj).length === 0) {
return true;
} else {
return false;
}
}
// Function to remove objects from body if blank
function clean(obj) {
for (var propName in obj) {
if (obj[propName] === "" || obj[propName] === null) {
delete obj[propName];
}
}
}
// Checking and Formatting Names Given
function capitalize(text) {
return text.replace(/\b\w/g, function(m) {
return m.toUpperCase();
});
}
if (body.firstName) {
body.firstName = capitalize(body.firstName);
}
if (body.lastName) {
body.lastName = capitalize(body.lastName);
}
// Checking and formatting email
if (body.email) {
body.email = body.email.toLowerCase();
body.email = body.email.trim();
// Checking for email in database
User.find({ email: body.email }, (err, EmailsFound) => {
if (EmailsFound.length > 0) {
var EmailsFoundErr = {
success: false,
message: "There is already an account with that email address"
};
hasErrors.errors = { ...hasErrors.errors, ...EmailsFoundErr };
}
});
}
// Getting User Session Token
UserSession.findById(updateUserInfo.sessionToken, function(err, userData) {
// Finding User ID using the current users session token
if (userData.isDeleted) {
var userDeletedError = {
success: false,
message:
"Your account is currently logged out, you must login to change account details"
};
hasErrors.errors = { ...hasErrors.errors, ...userDeletedError };
} else {
// Finding the user profile and updating fields that are present
User.findByIdAndUpdate(
userData.userId,
updateUserInfo.userInfo,
function(err, userInfo) {
// userInfo varable contains user db entry
if (err) {
var updateUserError = {
success: false,
message: "Error: Server Error"
};
hasErrors.errors = {
...hasErrors.errors,
...updateUserError
};
}
if (isEmpty(hasErrors.errors)) {
res.send({
success: true,
message: "Success: You have updated your profile!"
});
} else {
res.send({
success: false,
message: hasErrors.errors
});
}
}
);
}
});
});
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