Error handling patterns

What a session covers

The tutor works through these with you, in conversation and code. A session ends when you have shown them, not when a video does.

1. Explain when to throw an exception and when to return a result
2. Write a function that returns a result type for failures the caller must handle
3. Spot the catch that logs and carries on with a half-finished state

In practice

A few lines that show Error handling patterns doing its job.

type Result<T> = { ok: true; value: T } | { ok: false; error: string };

function parsePort(text: string): Result<number> {
  const n = Number(text);
  if (!Number.isInteger(n) || n < 1 || n > 65535) {
    return { ok: false, error: "port must be 1-65535, got " + text };
  }
  return { ok: true, value: n };
}

const port = parsePort(process.env.PORT ?? "");
if (!port.ok) throw new Error(port.error);

The common mistake

What to know first

Your roadmap puts these before Error handling patterns, unless you already know them.

• Promises and async/await

How it stays learned

Once a session shows you understand Error handling patterns, it comes back for review. Each review takes a minute and tells the memory model how well you still know it.

1. Day 3First recall, while it is fresh
2. Day 7Second, a week on
3. Day 18Last, when it has settled

Where it leads

Topics that build on Error handling patterns.

• Runtime validation