Handling Errors

Part of the Node.js Basics section of Coddy's Node.js journey. Lesson 13 of 24.

A notes.json edited by hand can break, and then JSON.parse throws and Node prints a stack trace.

try runs code that may throw. When it does, catch receives the error and your program decides what to say. err.message is the one-line reason.

let config;
try {
    config = JSON.parse('{ port: 3000 }');
} catch (err) {
    console.error(`config is broken: ${err.message}`);
    process.exit(1);
}

Do not catch the error and carry on with an empty list: the next add would save over the damaged file, and every note in it would be gone.

Challenge

Easy

When notes.json is not valid JSON, every command prints notes.json is damaged: <message> to stderr and exits with 1.
The starter's notes.json is damaged on purpose.

Run node notes.js list before and after your change. Then delete the extra comma in notes.json and run list again.

Try it yourself

import { existsSync, readFileSync, writeFileSync } from 'node:fs';

const file = 'notes.json';

const store = {
    notes: existsSync(file) ? JSON.parse(readFileSync(file, 'utf8')) : [],
    save() {
        writeFileSync(file, JSON.stringify(this.notes, null, 2));
    },
    add(text) {
        this.notes.push(text);
        this.save();
        return this.notes.length;
    },
    remove(n) {
        const [text] = this.notes.splice(n - 1, 1);
        this.save();
        return text;
    },
};

export default store;