方法在节点js中使用forEach循环进行云Firestore时给出空数组而不是完整数据

Question

I want a Fully response in JSON like,

[
   {
      "email":"a",
      "product":[
         {
            "price":100,
            "veg_name":"Potato",
            "stock":"10"
         },
         {
            "stock":"10",
            "price":"100",
            "veg_name":"Tomato"
         }
      ]
   },
   {
      "email":"amp",
      "product":[
         {
            "price":"1000",
            "veg_name":"ffdf"
         }
      ]
   }
]

This type of JSON data will store in fullDatas object in below code. on the fully completion of forEach loop. we can see this via console. But, Response in always like, [] means null.

let stockRef = firestore.collection('stock');
    const fullDatas = [];
    //stock
    let final = new Promise((resolve, reject) => {
        stockRef.get().then(documents => {
            documents.forEach(doc => {
                let data = {};
                //single select like 'a'
                data['email'] = doc.data()['email'];
                const product = [];

                let colRef = stockRef.doc(doc.id).collection('Product');
                colRef.get().then(vegDocs => {
                    vegDocs.forEach(veg => {
                        product.push(veg.data());
                    });
                    data['product'] = product;
                    fullDatas.push(data);
                    console.log(JSON.stringify(fullDatas));
                });
            });
            resolve(fullDatas);
        });
    });

    final.then((result) => {
        res.json(result);
    }).catch((error) => {
        res.send(error);
    });

What should I change in the above Code? I think I have implemented the wrong promise.

Answer 1

I can't make a comment because of reputation rule. However, I think the wrong is in this line

data['email'] = doc.data()['email'];

regarding your code doc.data() is an array with 2 element and you bass the key 'email' without determining which element you are want to access, so I think you need to make another loop here.

Answer 2

Rather using forEach and global/closure [] you can use Array.prototype.map .

You need to wait for each and every promise in the chain with return promise or await .

when you get an array of promises back from .map you can use Promise.all to wait for each and every promise to be resolved.

import { promises } from "fs";

let stockRef = firestore.collection('stock');
//stock
let final = stockRef.get().then(documents => {
    return documents.map(doc => {
        let data = {};
        //single select like 'a'
        data['email'] = doc.data()['email'];
        let colRef = stockRef.doc(doc.id).collection('Product');
        return colRef.get().then(vegDocs => {
            const productPromises = vegDocs.map(veg => veg.data());
            return Promise.all(productPromises).then(product => data['product'] = product);
        }).then(() => data);
    });
}).then(Promise.all);

final.then((result) => {
    res.json(result);
}).catch((error) => {
    res.send(error);
});

Answer 3

By Reading a document reference. I have replacing forEach to for loop and also placed a proper async/await and proper use of Promise.

let stockRef = firestore.collection('stock');
    const fullDatas = [];
    //stock
    let final = new Promise((resolve, reject) => {
        stockRef.get().then(async documents => {
            let docs = documents.docs;
            for (let doc of docs) {
                console.log(doc.data());
                let data = {};
                //single select like 'a'
                data['email'] = doc.data()['email'];
                const product = [];

                let colRef = stockRef.doc(doc.id).collection('Product');
                await colRef.get().then(vegSnapshot => {
                    let vegDocs = vegSnapshot.docs;
                    for (let veg of vegDocs) {
                        product.push(veg.data());
                    }
                    data['product'] = product;
                    fullDatas.push(data);
                    console.log(JSON.stringify(fullDatas));
                });
            }
            resolve(fullDatas);
        });
    });

    final.then((result) => {
        res.json(result);
    }).catch((error) => {
        res.send(error);
    });