Try It Yourself - SyntaxStudy Editor

HTML / CSS / JS

// Pattern 1 – manual try/catch (always safe)
app.get('/a', async (req, res, next) => {
    try {
        const data = await fetchData();
        res.json(data);
    } catch (err) {
        next(err); // forward to error handler
    }
});

// Pattern 2 – asyncHandler wrapper (DRY)
const asyncHandler = fn => (req, res, next) =>
    Promise.resolve(fn(req, res, next)).catch(next);

app.get('/b', asyncHandler(async (req, res) => {
    const data = await fetchData(); // any throw is caught
    res.json(data);
}));

// Pattern 3 – express-async-errors package (global patch)
require('express-async-errors'); // patch Express once
app.get('/c', async (req, res) => {
    const data = await fetchData(); // no wrapper needed
    res.json(data);
});

// Process-level safety net
process.on('unhandledRejection', (reason) => {
    console.error('Unhandled Rejection:', reason);
    process.exit(1); // let PM2/Kubernetes restart
});
process.on('uncaughtException', (err) => {
    console.error('Uncaught Exception:', err);
    process.exit(1);
});