How to read and write into file using JavaScript?

Question

Can anybody give some sample code to read and write a file using JavaScript?

Answer 1

From a ReactJS test, the following code successfully writes a file:

import writeJsonFile from 'write-json-file';

const ans = 42;
writeJsonFile('answer.txt', ans);

const json = {"answer": ans};
writeJsonFile('answer_json.txt', json);

The file is written to the directory containing the tests, so writing to an actual JSON file '*.json' creates a loop!