JavaScript Error Handling — try/catch Done Right

Errors are not failures — unhandled errors are. Production code differs from tutorial code mostly in how it handles the unhappy path.

The mechanics

try {
  const data = JSON.parse(raw);        // may throw
} catch (err) {
  console.error(err.name, err.message); // SyntaxError, "Unexpected token..."
} finally {
  spinner.hide();                       // ALWAYS runs — cleanup goes here
}

Throw meaningful errors

function setMarks(m) {
  if (m < 0 || m > 100) throw new RangeError(`Invalid marks: ${m}`);
}

class ApiError extends Error {
  constructor(status, msg) { super(msg); this.name = "ApiError"; this.status = status; }
}

What a good catch block does

• Shows the user something actionable ("Could not save — retry?")
• Logs details for debugging
• Never swallows silently — an empty catch is a future 3am bug hunt

Async errors

await inside try/catch catches rejected promises. Without await, use .catch() — an unhandled rejection crashes Node processes.