Q1. How do you read a JSON file in Node.js?
Read the file with fs.readFile(), then parse with JSON.parse(). Example:
fs.readFile('data.json', 'utf8', (err, data) => {
if (err) throw err;
const obj = JSON.parse(data);
console.log(obj);
});
const data = require('./data.json')
Q2. How do you write a JSON file?
Convert object to JSON string with JSON.stringify(), then write with fs.writeFile(). Example:
const obj = { name: 'John', age: 30 };
const json = JSON.stringify(obj, null, 2); // pretty print
fs.writeFile('output.json', json, (err) => {
// ...
});
Q3. How do you update a JSON file?
Read the file, parse, modify the object, then write back. Example:
fs.readFile('data.json', (err, data) => {
const obj = JSON.parse(data);
obj.newProp = 'value';
fs.writeFile('data.json', JSON.stringify(obj, null, 2), (err) => {
// ...
});
});
Q4. What are the advantages of using require() for JSON?
require('./file.json') automatically parses JSON and returns the object. It's synchronous and caches the result, so subsequent requires don't read the file again. This is convenient for configuration files that don't change during runtime. However, for dynamic JSON, use fs methods.
Q5. How do you handle JSON parsing errors?
Wrap JSON.parse() in try/catch. Example:
try {
const obj = JSON.parse(data);
} catch (err) {
if (err instanceof SyntaxError) {
console.error('Invalid JSON');
} else {
throw err;
}
}