Node.Js write and read Array to/from File

Question

i have a NodeJs applet that I want to save the Users Array (Contains Objects) to a File, I am doing this with:

const fs = require('fs');
const util = require('util');
fs.writeFileSync('data/inventur_users.json', util.inspect(users), 'utf-8');

The Output in the File inventur_Users.json is:

[ BU4AFLx3cUYqdjvYPci7: { id: '5LkOWtVFcqz29UpsAAAC',
    name: '[email protected]',
    rechte: 'vollzugriff',
    client_ID: 'BU4AFLx3cUYqdjvYPci7' } ]

Now I am Reading the file back in with this code:

filedata = fs.readFileSync('data/inventur_users.json', 'utf-8');

My Problem is that i only get a String and I don't know how to convert the String back to an Array that contains Objects.

Thanks in advance, Patrick

namar sood · Accepted Answer · 2020-06-25 11:22:33Z

1

Firstly

[ BU4AFLx3cUYqdjvYPci7: { id: '5LkOWtVFcqz29UpsAAAC',
    name: '[email protected]',
    rechte: 'vollzugriff',
    client_ID: 'BU4AFLx3cUYqdjvYPci7' } ]

is not a valid json, you can verify it from here https://jsonlint.com/

Valid json would look like

[{
    "BU4AFLx3cUYqdjvYPci7": {
        "id": "5LkOWtVFcqz29UpsAAAC",
        "name": "[email protected]",
        "rechte": "vollzugriff",
        "client_ID": "BU4AFLx3cUYqdjvYPci7"
    }
}]

and then you can directly require content of .json file in a variable like

const filedata = require('data/inventur_users.json');

answered Jun 25, 2020 at 11:22

namar sood

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15 Comments

Patrick Langkau Over a year ago

Thank you for your reply, how can i convert an array to a json? And if i Import the json, can i use it like i used the array? Patrick

namar sood Over a year ago

[1, 2, 3] is a valid json so you can store it directly in json file and while requiring it, yes you can use it directly like an array. You can use jsonlint.com to verify what is valid json and what is not

Patrick Langkau Over a year ago

So i was able to export the Array to a valid Json, but if i want to import it with require i get this error: 'Error: Cannot find module 'data/inventur_users.json' but the json is in that directory

namar sood Over a year ago

try with require('./data/inventur_users.json');

Patrick Langkau Over a year ago

Now i can read the json but it gives me a string of the json without the " at the beginning and the end

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AcruxCode · Accepted Answer · 2020-06-25 11:25:46Z

0

You can use JSON.parse() to convert the string back to a JavaScript object:

filedata = JSON.parse(fs.readFileSync('data/inventur_users.json', 'utf-8'));

You should also use JSON.stringify() to save the file in the first place:

fs.writeFileSync('data/inventur_users.json', JSON.stringify(util.inspect(users)), 'utf-8');

answered Jun 25, 2020 at 11:25

AcruxCode

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3 Comments

Patrick Langkau Over a year ago

I did it like in your example but filedata is still a string.

AcruxCode Over a year ago

Have you also used JSON.stringify(...) to save the file?

Patrick Langkau Over a year ago

Here you can see the code, json and output: pastebin.com/nZqZNdpy

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