How to push json data from a json file into an array with a new set and update the file

Question

I am using node js and trying to save a set of JSON data into file.

const products = [];
    fs.readFile(pathToTheFile, (err, data) => { // get the data from the file
        if(data != ''){
            products.push(JSON.parse(data)); // the data is in string format. convert it into JSON and push into the empty arry of products
        }
        products.push(this); // push the form data in to products array after the file data
        fs.writeFile(pathToTheFile, JSON.stringify(products), (err) => { // convert the products array back into string and update the file entirely with the data
            console.log(err);
        });            
    });

But the JSON data is being saved in the file like this in nested way.

[
[
    [
        {
            "title": "1",
            "imageUrl": "https://images.pexels.com/photos/279906/pexels-photo-279906.jpeg?cs=srgb&dl=pexels-pixabay-279906.jpg&fm=jpg",
            "description": "wer",
            "price": "1234"
        }
    ],
    {
        "title": "2",
        "imageUrl": "https://images.pexels.com/photos/279906/pexels-photo-279906.jpeg?cs=srgb&dl=pexels-pixabay-279906.jpg&fm=jpg",
        "description": "er3t",
        "price": "21345"
    }
],
{
    "title": "3",
    "imageUrl": "https://images.pexels.com/photos/279906/pexels-photo-279906.jpeg?cs=srgb&dl=pexels-pixabay-279906.jpg&fm=jpg",
    "description": "wew",
    "price": "2345"
}

]

What shall I do in this case?

Edit:

The this is coming from my class contructor

    constructor(title, imageUrl, description, price) {
    this.title = title;
    this.imageUrl = imageUrl;
    this.description = description;
    this.price = price;
}

I tried with concat like this

 const products = [];
    fs.readFile(pathToTheFile, (err, data) => { // get the data from the file
        if (data != '') {
            products.push(JSON.parse(data)); // the data is in string format. convert it into JSON and push into the empty arry of products
            //console.log(this);
            products.concat(this);
        } else {
            products.push(this); // push the form data in to products array after the file data
        }
        console.log(products);
        fs.writeFile(pathToTheFile, JSON.stringify(products), (err) => { // convert the products array back into string and update the file entirely with the data
            console.log(err);
        });
    });

But getting an empty array

[
[
    {
        "title": "",
        "imageUrl": "",
        "description": "",
        "price": ""
    }
]

]

What is the value of the data and this variable? What is the value of the products variable before you write it to the file? Try to add some console.logs. — Molda
– Molda, Commented Aug 7, 2021 at 9:20

Gilles Heinesch · Accepted Answer · 2022-03-17 21:07:37Z

1

You are inserting an array into the product array.
See the correct code below -

const products = [];
    fs.readFile(pathToTheFile, (err, data) => { // get the data from the file
        if(data != ''){
            products = JSON.parse(data);
        }
        products.push(this);
        fs.writeFile(pathToTheFile, JSON.stringify(products), (err) => {
            console.log(err);
        });            
    });

edited Mar 17, 2022 at 21:07

Gilles Heinesch

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answered Aug 7, 2021 at 9:34

Gaurav Sharma

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3 Comments

Shubhajit Halder Over a year ago

this one worked. thank you. But I had to change const product = [] to let product =[]. Can you please explain this line? products = JSON.parse(data));

Gaurav Sharma Over a year ago

Do you need the products as a global variable? Otherwise, you can use declare products as const inside arrow function.

Shubhajit Halder Over a year ago

Never mind. Got it. I was inserting the data. I had to store it.

Suyash Gaur · Accepted Answer · 2021-08-07 09:21:31Z

0

Instead of push() you should use concat() method.

push() : The push() method adds one or more elements to the end of an array and returns the new length of the array. (MDN)

var arr1 = [‘a’, ‘b’, ‘c’];
var arr2 = [‘d’, ‘e’, ‘f’];
var arr3 = arr1.push(arr2);
console.log(arr3); // 4
console.log(arr1); // [“a”,> “b”, “c”, [“d”, “e”, “f”]]

concat() : The concat() method is used to merge two or more arrays. This method does not change the existing arrays, but instead returns a new array.

var arr1 = [‘a’, ‘b’, ‘c’];
var arr2 = [‘d’, ‘e’, ‘f’];
var arr3 => arr1.concat(arr2);
console.log(arr3); //[“a”, “b”, “c”, “d”, “e”, “f”]

answered Aug 7, 2021 at 9:21

Suyash Gaur

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1 Comment

Shubhajit Halder Over a year ago

tried concat. edited the question with my try with concat

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