这个JavaScript对象是如何转换成字符串的？

我一直在为产品目录系统开发Node.JS/MongoDB后端，我遇到了一个奇怪的bug

过程 首先，我从产品集合中加载产品信息。此产品包含名称、说明等信息，还包含指向字符串数组中产品图像的文件上载ID列表。 然后，对于每个上传ID，加载每个照片的信息。然后，我将upload ID字符串数组替换为文件信息对象数组。 但是，当我输出结果产品对象时，图像列表是一个字符串列表，表示JavaScript，就好像它们是用代码编写的一样

代码 Mongoose架构文件：

// file.model.js
getByUploadId: function(uploadId) {
    return this.findOne({
        uploadId
    });
}

我不明白，当我将

productRecord.images

属性设置为

imageInfo

时，数组中的值突然变成了值的字符串表示形式。

该字符串不包含JSON，而是包含一个可读的字符串表示，表示对象如何硬编码为JavaScript。这些字符串根本无法解析为JSON。JSON希望将键包装在双引号中，而生成的JavaScript代码没有这样的内容

---

发生这种情况有什么原因吗？我从未见过这种情况。

问题是由于猫鼬模式造成的，它们通过模式中声明的类型保护模型。find返回的对象是一个mongoose模型，当您更新其上的任何值时，它们会进行类型检查

让我们来看看你的场景。我创造了一个例子。见下文

    const mongoose = require('mongoose');
    const db = require('./db');
    const Schema = mongoose.Schema;

    const productSchema = new Schema({
      name: {type: String},
      images: [String]  // Note schema have array of string
    });

    const productModel = mongoose.model('product', productSchema);

    db.connect().then(() => {
      //find record from productSchema
      return productModel.find({})
        .then((productRecords) => { //productRecords - don't forget is a mongoose model object

// productRecords from db  [{"name":"gilette","images":["idx","idy"],"_id":"5ac324c4fad317265b9df226","__v":0}]


          //TRIAL A
          for (let productRecordI in productRecords) {
            productRecords[productRecordI] = populateImageInformation(productRecords[productRecordI]);

          }
          console.log(typeof productRecords[0].images[0]); //=> string;


          //SOLUTION for the problem is copy mongoose data without reference
          //TRIAL B
          productRecords = JSON.parse(JSON.stringify(productRecords));
          for (let productRecordI in productRecords) {
            productRecords[productRecordI] = populateImageInformation(productRecords[productRecordI]);

          }
          console.log(typeof productRecords[0].images[0]); //=> Object;

        });

      //just a mock function change images to object
      function populateImageInformation(productRecord) {
        imageInfo = [];
        for (let uploadId of productRecord.images) {
          let imageData = {name: uploadId};
          imageInfo.push(imageData);
          console.log(typeof imageData); // => object
        }
        productRecord.images = imageInfo;
        return productRecord;
      }


    }).catch((err) => {
      console.log('err', err);
    });

---

可能是这样，但..productRecord.images是字符串数组。。。因此，可能是将对象转换为字符串以匹配typesJavaScript不关心类型，我甚至在设置数组之前尝试删除它，但它没有改变任何东西可能res.json有副作用？它做什么？

res.json

在这里没有效果。数据在发送回浏览器之前被篡改。问题中缺少产品的架构。

    const mongoose = require('mongoose');
    const db = require('./db');
    const Schema = mongoose.Schema;

    const productSchema = new Schema({
      name: {type: String},
      images: [String]  // Note schema have array of string
    });

    const productModel = mongoose.model('product', productSchema);

    db.connect().then(() => {
      //find record from productSchema
      return productModel.find({})
        .then((productRecords) => { //productRecords - don't forget is a mongoose model object

// productRecords from db  [{"name":"gilette","images":["idx","idy"],"_id":"5ac324c4fad317265b9df226","__v":0}]


          //TRIAL A
          for (let productRecordI in productRecords) {
            productRecords[productRecordI] = populateImageInformation(productRecords[productRecordI]);

          }
          console.log(typeof productRecords[0].images[0]); //=> string;


          //SOLUTION for the problem is copy mongoose data without reference
          //TRIAL B
          productRecords = JSON.parse(JSON.stringify(productRecords));
          for (let productRecordI in productRecords) {
            productRecords[productRecordI] = populateImageInformation(productRecords[productRecordI]);

          }
          console.log(typeof productRecords[0].images[0]); //=> Object;

        });

      //just a mock function change images to object
      function populateImageInformation(productRecord) {
        imageInfo = [];
        for (let uploadId of productRecord.images) {
          let imageData = {name: uploadId};
          imageInfo.push(imageData);
          console.log(typeof imageData); // => object
        }
        productRecord.images = imageInfo;
        return productRecord;
      }


    }).catch((err) => {
      console.log('err', err);
    });