How can I save a JSON object to a file using JavaScript?

JSON objects are a common way to store and exchange data. It's often useful to save a JSON object to a file, either in a Node.js environment or in the browser. Luckily, neither one is particularly difficult.

Pretty-print JSON

Pretty-printing JSON objects in pretty easy and customizable in JavaScript. Here's the gist of it.

Save a JSON object to a file in Node.js

Node.js provides a built-in module called fs that allows you to work with the file system. You can use the fs.writeFileSync() method to write a JSON object to a file. To convert the JSON object to a string, you can use JSON.stringify(). Finally, you should specify the file extension as .json.

import { writeFileSync } from 'fs';

const JSONToFile = (obj, filename) =>
  writeFileSync(`${filename}.json`, JSON.stringify(obj, null, 2));

JSONToFile({ test: 'is passed' }, 'testJsonFile');
// writes the object to 'testJsonFile.json'

Save a JSON object to a file in the browser

In the browser, you can use the Blob and URL.createObjectURL() to create a downloadable file. You can the use Document.createElement() to create an anchor element (a), set its href and download attributes, and then trigger a click event to download the file.

const JSONToFile = (obj, filename) => {
  const blob = new Blob([JSON.stringify(obj, null, 2)], {
    type: 'application/json',
  });
  const url = URL.createObjectURL(blob);
  const a = document.createElement('a');
  a.href = url;
  a.download = `${filename}.json`;
  a.click();
  URL.revokeObjectURL(url);
};

JSONToFile({ test: 'is passed' }, 'testJsonFile');
// downloads the object as 'testJsonFile.json'