如何解决得到！错误[ERR_HTTP_HEADERS_SENT]：将标头发送到客户端后，无法设置标头|表现
我收到错误[ERR_HTTP_HEADERS_SENT]：将标头发送到客户端后无法设置标头，然后在执行POST请求时将一些带有错误位置的长列表称为快速路由。我看到了类似的答案，有很多答案，但我找不到我想念的地方。
在这里，我附上了该特定POST请求的代码示例。
.post(cors.corsWithOptions,authenticate.verifyUser,(req,res,next) => {
Favorites.findOne({user: req.user._id})
.then((favs)=> {
if(!favs) {
Favorites.create({user: req.user._id,dishes: req.body})
.then((favs)=> {
console.log('Favs created: ',favs);
res.statusCode = 200;
res.setHeader('Content-Type','application/json');
res.json(favs);
},(err) => next(err))
.catch((err) => next(err));
}
else {
var noofids = req.body.length;
for (var i=0; i<noofids ; i++) {
if(favs.dishes.indexOf(req.body[i]._id) > -1) {
res.json('It is already in the dishes');
}
else {
favs.dishes.push(req.body[i]._id);
favs.save()
.then((doc) => {
Favorites.findById(doc._id)
.populate('User').populate('Dishes')
.then((fav) => {
res.statusCode = 200;
res.setHeader('Content-Type','application/json');
res.json(fav);
},(err) => next(err))
.catch((err) => next(err));
},(err) => next(err))
.catch((err) => next(err));
}
}
}
},(err) => next(err))
.catch((err) => next(err));
})
执行 if 部分时，它会执行无错误，但是执行 else 时，它将显示一长串错误。
POST /favorites/ 200 7.864 ms - 29
Error [ERR_HTTP_HEADERS_SENT]: Cannot set headers after they are sent to the client
at ServerResponse.setHeader (_http_outgoing.js:518:11)
at ServerResponse.header (E:\CourseraMERN\NodeJS\conFusionServer\node_modules\express\lib\response.js:767:10)
at ServerResponse.send (E:\CourseraMERN\NodeJS\conFusionServer\node_modules\express\lib\response.js:170:12)
at done (E:\CourseraMERN\NodeJS\conFusionServer\node_modules\express\lib\response.js:1004:10)
at Object.exports.renderFile (E:\CourseraMERN\NodeJS\conFusionServer\node_modules\jade\lib\index.js:374:12)
at View.exports.__express [as engine] (E:\CourseraMERN\NodeJS\conFusionServer\node_modules\jade\lib\index.js:417:11)
at View.render (E:\CourseraMERN\NodeJS\conFusionServer\node_modules\express\lib\view.js:135:8)
at tryRender (E:\CourseraMERN\NodeJS\conFusionServer\node_modules\express\lib\application.js:640:10)
at Function.render (E:\CourseraMERN\NodeJS\conFusionServer\node_modules\express\lib\application.js:592:3)
at ServerResponse.render (E:\CourseraMERN\NodeJS\conFusionServer\node_modules\express\lib\response.js:1008:7)
at E:\CourseraMERN\NodeJS\conFusionServer\app.js:84:7
at Layer.handle_error (E:\CourseraMERN\NodeJS\conFusionServer\node_modules\express\lib\router\layer.js:71:5)
at trim_prefix (E:\CourseraMERN\NodeJS\conFusionServer\node_modules\express\lib\router\index.js:315:13)
at E:\CourseraMERN\NodeJS\conFusionServer\node_modules\express\lib\router\index.js:284:7
at Function.process_params (E:\CourseraMERN\NodeJS\conFusionServer\node_modules\express\lib\router\index.js:335:12)
at next (E:\CourseraMERN\NodeJS\conFusionServer\node_modules\express\lib\router\index.js:275:10)
如何纠正此问题？谢谢！
解决方法
请确保每个return语句都res.json()，否则代码将继续执行其下的行，并且您具有在多个位置设置标题的代码，这会导致错误：
.post(cors.corsWithOptions,authenticate.verifyUser,(req,res,next) => {
Favorites.findOne({user: req.user._id})
.then((favs)=> {
if(!favs) {
Favorites.create({user: req.user._id,dishes: req.body})
.then((favs)=> {
console.log('Favs created: ',favs);
res.statusCode = 200;
res.setHeader('Content-Type','application/json');
return res.json(favs);
},(err) => next(err))
.catch((err) => next(err));
}
else {
var noofids = req.body.length;
for (var i=0; i<noofids ; i++) {
if(favs.dishes.indexOf(req.body[i]._id) > -1) {
return res.json('It is already in the dishes');
}
else {
favs.dishes.push(req.body[i]._id);
favs.save()
.then((doc) => {
Favorites.findById(doc._id)
.populate('User').populate('Dishes')
.then((fav) => {
res.statusCode = 200;
res.setHeader('Content-Type','application/json');
return res.json(fav);
},(err) => next(err))
.catch((err) => next(err));
},(err) => next(err))
.catch((err) => next(err));
}
}
}
},(err) => next(err))
.catch((err) => next(err));
})
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