Template cannot be rendered due to the joint query of populate in mongoose: syntax error: unexpected token r in JSON at position 0

Error information

Error code

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

Error reason

When the populate </ code> method is used in mongoose to realize the set association, the template engine cannot render. This is because when the set joint query and rendering page template are carried out at the same time, the two conflicts will result in the failure of rendering the page. For example, we change the above code to the following:

    let articles = await Article.find().populate('author');
    res.send('ok');    // The server side can respond to the client ok so there is a real conflict between template rendering and federated queries

resolvent

Using the lean () method

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

Lean() method: it tells mongoose to return a normal object instead of a mongoose document object, which is used internally first JSON.stringify () this method converts the document object to a string, removes all other attribute formats, and then leaves only the required data string~

Using stringfy() and parse() methods

And the above method is essentially the same

    let articles = await Article.find().populate('author');
    let str = JSON.stringify(result);
    let json = JSON.parse(str);
    res.render('admin/article', { json });

When we continue the paging function, we use the JSON method

To achieve paging function, we use the mongoose sex page </ code> third-party module for paging, and then we change 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 });

The problem will be solved πŸ˜€

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