How do i create a JSON file from an array in JavaScript?

Question

I'm working on a Node.js project using JavaScript. My issue is that I have an array with some data, and i want to use this data in the array to create a JSON file.

This is what I have:

var cars = ["Saab", "Volvo", "BMW"];

This is what I want:

{
  "cars": [
    {
       "mark" : "Saab"
    },
    {
       "mark" : "Volvo"
    },
    {
       "mark" : "BMW"
    }
  ]
}

Java has a library called Jackson which helps with this. Does Node.js not have something similar?

Please if the question does not live up to the rules, let me know.

Terry Lennox · Accepted Answer · 2020-02-28 08:32:50Z

This is very simple indeed in Node.js, you can use the JSON methods stringify and parse to create strings from objects and arrays. We can first use reduce to create a car object from the car array.

I'm using JSON.stringify() with null, 4 as the last arguments to pretty-print to the file. If we wanted to print everything to one line, we'd just use JSON.stringify(carObj).

For example:

const fs = require("fs");

const cars =  ["Saab", "Volvo", "BMW"];
const carObj =  cars.reduce((map, car) => { 
    map.cars.push( { mark: car} );
    return map;
}, { cars: []})

// Write cars object to file..
fs.writeFileSync("./cars.json", JSON.stringify(carObj, null, 4));

// Read back from the file...
const carsFromFile = JSON.parse(fs.readFileSync("./cars.json", "utf8"));
console.log("Cars from file:", carsFromFile);

The cars.json file will look like so:

{
    "cars": [
        {
            "mark": "Saab"
        },
        {
            "mark": "Volvo"
        },
        {
            "mark": "BMW"
        }
    ]
}

EugenSunic · Accepted Answer · 2020-02-28 08:21:07Z

3

var cars = ["Saab", "Volvo", "BMW"];


const result = cars.reduce((acc, x) => {
  acc.cars.push({
    mark: x
  })
  return acc;
}, {
  cars: []
})
console.log(result)

answered Feb 28, 2020 at 8:21

EugenSunic

13.8k15 gold badges68 silver badges96 bronze badges

Collectives™ on Stack Overflow

How do i create a JSON file from an array in JavaScript?

2 Answers 2

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related