Javascript 发送POST请求后出错：发送到客户端后无法设置标头

我找不到我的代码有什么问题。。。！当我发送post请求时，得到一个错误：“发送到客户端后无法设置头” 我的模型是-在那里我创建了评论模式，而我有用户、内容、博客

    const mongoose = require("mongoose");
const { ObjectId } = mongoose.Schema;

const comment_schema = new mongoose.Schema(
  {
    user: {
      type: String,
      required: true,
    },
    content: {
      type: String,
      required: true,
    },
    blog: {
      type: mongoose.Schema.Types.ObjectId,
      ref: "Blog",
    },
  },
  { timestamps: true }
);

const Comment = mongoose.model("Comment", comment_schema);
module.exports = Comment;

控制器是-这是我的postComment控制器，首先我使用req.params.blogId找到一个博客，然后我创建一个评论并保存它。。！最后将帖子与评论联系起来

exports.postComment = async (req, res) => {
  /// Find A Blog
  const blog = await Blog.findOne({ _id: req.params.blogId });
  // console.log(blog);
  // console.log(req.params.blogId);
  /// Create A Comment
  const comment = new Comment();
  comment.content = req.body.content;
  comment.user = req.body.user;
  // console.log(req.body.user);
  comment.blog = blog._id;
  comment.save((err, Blog_comment) => {
    if (err) {
      return res.status(400).json({
        error: "something went wrong please try again ..!",
      });
    }
    res.json({ Blog_comment });
  });
  /// Associate Post with comment
  blog.comment.push(comment._id);
  blog.save((err, comment) => {
    if (err) {
      res.status(400).json({
        error: "Saving Comment in DB failed",
      });
    }
    // res.status(200).json(comment);
    res.send(comment);
  });
  // res.send(comment);
};

路由器是-这是我的POST路由器（）

完全错误-我不明白为什么会出现此错误

events.js:292
      throw er; // Unhandled 'error' event
      ^

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:\git\backend\node_modules\express\lib\response.js:771:10)
    at ServerResponse.send (E:\git\backend\node_modules\express\lib\response.js:170:12)
    at ServerResponse.json (E:\git\backend\node_modules\express\lib\response.js:267:15)
    at ServerResponse.send (E:\git\backend\node_modules\express\lib\response.js:158:21)
    at E:\git\backend\controllers\blog.js:196:9
    at E:\git\backend\node_modules\mongoose\lib\model.js:4842:16
    at E:\git\backend\node_modules\mongoose\lib\helpers\promiseOrCallback.js:24:16
    at E:\git\backend\node_modules\mongoose\lib\model.js:4865:21
    at model.<anonymous> (E:\git\backend\node_modules\mongoose\lib\model.js:502:7)
    at E:\git\backend\node_modules\kareem\index.js:315:21
    at next (E:\git\backend\node_modules\kareem\index.js:209:27)
    at E:\git\backend\node_modules\kareem\index.js:182:9
    at E:\git\backend\node_modules\kareem\index.js:507:38
    at processTicksAndRejections (internal/process/task_queues.js:79:11) 
Emitted 'error' event on Function instance at:
    at E:\git\backend\node_modules\mongoose\lib\model.js:4844:13
    at E:\git\backend\node_modules\mongoose\lib\helpers\promiseOrCallback.js:24:16
    [... lines matching original stack trace ...]
    at processTicksAndRejections (internal/process/task_queues.js:79:11) 
{
  code: 'ERR_HTTP_HEADERS_SENT'
}
[nodemon] app crashed - waiting for file changes before starting...      

events.js:292
投掷者；//未处理的“错误”事件
^
错误[ERR\u HTTP\u HEADERS\u SENT]：发送到后无法设置头
客户
在ServerResponse.setHeader（_http_outgoing.js:518:11）
在ServerResponse.header（E:\git\backend\node\u modules\express\lib\response.js:771:10）
在ServerResponse.send（E:\git\backend\node\u modules\express\lib\response.js:170:12）
在ServerResponse.json（E:\git\backend\node\u modules\express\lib\response.js:267:15）
在ServerResponse.send（E:\git\backend\node\u modules\express\lib\response.js:158:21）
在E:\git\backend\controllers\blog.js:196:9
位于E:\git\backend\node\u modules\mongoose\lib\model.js:4842:16
在E:\git\backend\node\u modules\mongoose\lib\helpers\promiseOrCallback.js:24:16
位于E:\git\backend\node\u modules\mongoose\lib\model.js:4865:21
在模型上。（E:\git\backend\node\u modules\mongoose\lib\model.js:502:7）
在E:\git\backend\node\u modules\kareem\index.js:315:21
下一步（E:\git\backend\node\u modules\kareem\index.js:209:27）
在E:\git\backend\node\u modules\kareem\index.js:182:9
在E:\git\backend\node\u modules\kareem\index.js:507:38
在处理和拒绝时（内部/process/task_queues.js:79:11）
在以下位置对函数实例发出“错误”事件：
位于E:\git\backend\node\u modules\mongoose\lib\model.js:4844:13
在E:\git\backend\node\u modules\mongoose\lib\helpers\promiseOrCallback.js:24:16
[…与原始堆栈跟踪匹配的行…]
在处理和拒绝时（内部/process/task_queues.js:79:11）
{
代码：“ERR\u HTTP\u HEADERS\u SENT”
}
[nodemon]应用程序崩溃-正在等待文件更改，然后再启动。。。

---

有人能帮忙吗。。。！请帮助我无法解决这个问题。。。！请帮助

以下是脚本的解决方案，只有在执行所有操作或引发第一个错误时，才会将响应发送到浏览器：

exports.postComment=async（req，res）=>{
试一试{
///查找博客
让blog=wait blog.findOne（{u id:req.params.blogId}）；
///创建注释
让注释=新注释（）；
comment.content=req.body.content；
comment.user=req.body.user；
comment.blog=blog.\u id；
comment=comment.save（）；
///将帖子与评论联系起来
blog.comment.push（comment.\u id）；
blog=等待blog.save（）；
res.send（博客）；
}捕捉（错误）{
res.status（400）.json({
错误：“在数据库中保存注释失败”，
});
}
};

一旦响应发送到请求，您将再次发送响应。您可以在comment.save回调和blog.save回调中观察到这一点。您可以对请求响应一次。

events.js:292
      throw er; // Unhandled 'error' event
      ^

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:\git\backend\node_modules\express\lib\response.js:771:10)
    at ServerResponse.send (E:\git\backend\node_modules\express\lib\response.js:170:12)
    at ServerResponse.json (E:\git\backend\node_modules\express\lib\response.js:267:15)
    at ServerResponse.send (E:\git\backend\node_modules\express\lib\response.js:158:21)
    at E:\git\backend\controllers\blog.js:196:9
    at E:\git\backend\node_modules\mongoose\lib\model.js:4842:16
    at E:\git\backend\node_modules\mongoose\lib\helpers\promiseOrCallback.js:24:16
    at E:\git\backend\node_modules\mongoose\lib\model.js:4865:21
    at model.<anonymous> (E:\git\backend\node_modules\mongoose\lib\model.js:502:7)
    at E:\git\backend\node_modules\kareem\index.js:315:21
    at next (E:\git\backend\node_modules\kareem\index.js:209:27)
    at E:\git\backend\node_modules\kareem\index.js:182:9
    at E:\git\backend\node_modules\kareem\index.js:507:38
    at processTicksAndRejections (internal/process/task_queues.js:79:11) 
Emitted 'error' event on Function instance at:
    at E:\git\backend\node_modules\mongoose\lib\model.js:4844:13
    at E:\git\backend\node_modules\mongoose\lib\helpers\promiseOrCallback.js:24:16
    [... lines matching original stack trace ...]
    at processTicksAndRejections (internal/process/task_queues.js:79:11) 
{
  code: 'ERR_HTTP_HEADERS_SENT'
}
[nodemon] app crashed - waiting for file changes before starting...