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Private project practice sharing populate joint query in mongoose makes the template unable to render - solve the error message: syntaxerror: unexpected token r in JSON at

2022-07-03 23:46:00 【That's a simple man】

Error message

# Share the actual operation of private items # stay mongoose In the middle of populate The union query causes the template to fail to render —— How to solve the problem of misinformation ：SyntaxError: Unexpected token R in JSON at_nodeJS

Error code

       
       let 
       
       articles 
       
       = 
       
       await 
       
       Article.
       
       find().
       
       populate(
       
       'author');
       
       res.
       
       render(
       
       'admin/article', { 
       
       articles });
      
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2.

Cause of error

stay mongoose Use in populate Method to implement Collection Association , Causes the template engine to fail to render , This is because when the collection jointly queries and renders the page template at the same time, they will conflict , As a result, the page cannot be rendered , For example, let's change the above code to something like this ：

       
       let 
       
       articles 
       
       = 
       
       await 
       
       Article.
       
       find().
       
       populate(
       
       'author');
       
       res.
       
       send(
       
       'ok');    
       
       //  The server can respond to the client  ok  So template rendering does conflict with federated queries 
      
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resolvent

Use lean() Method

       
       let 
       
       articles 
       
       = 
       
       await 
       
       Article.
       
       find().
       
       populate(
       
       'author').
       
       lean();
       
       res.
       
       render(
       
       'admin/article', { 
       
       articles });
      
1.
2.

lean() Method ： Is to tell mongoose Returns a normal object , instead of mongoose Document object , Method internal first use JSON.stringify() This method converts the document object to a string , Remove all other attribute formats , Then leave only the data string you need ~

Use stringfy（） and parse（） Method

It's essentially the same as the above method .

       
       let 
       
       articles 
       
       = 
       
       await 
       
       Article.
       
       find().
       
       populate(
       
       'author');
       
       let 
       
       str 
       
       = 
       
       JSON.
       
       stringify(
       
       result);
       
       let 
       
       json 
       
       = 
       
       JSON.
       
       parse(
       
       str);
       
       res.
       
       render(
       
       'admin/article', { 
       
       json });
      
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While continuing with paging , We use JSON Method

When it comes to paging , We used mongoose-sex-page Third party module pagination , Then we changed the code to ：

       
       let 
       
       temp 
       
       = 
       
       await 
       
       pagination(
       
       Article).
       
       find({})
       
    .
       
       page(
       
       page)
       
    .
       
       size(
       
       2)
       
    .
       
       display(
       
       2).
       
       populate(
       
       'author')
       
    .
       
       exec();
       
       let 
       
       str 
       
       = 
       
       JSON.
       
       stringify(
       
       temp);
       
       let 
       
       articles 
       
       = 
       
       JSON.
       
       parse(
       
       str);
       
       res.
       
       render(
       
       'admin/article', { 
       
       articles });
      
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