effect-patterns-getting-started

Effect-TS Patterns: Getting Started

This skill provides 6 curated Effect-TS patterns for getting started. Use this skill when working on tasks related to:

• getting started
• Best practices in Effect-TS applications
• Real-world patterns and solutions

---

🟢 Beginner Patterns

Retry a Failed Operation with Effect.retry

Rule: Retry failed operations with Effect.retry.

Good Example:

import { Effect, Schedule, pipe } from "effect";

class ApiError {
  readonly _tag = "ApiError";
  constructor(readonly status: number) {}
}

const fetchUserData = (userId: string) =>
  Effect.tryPromise({
    try: async () => {
      const response = await fetch(`/api/users/${userId}`);
      if (!response.ok) throw new ApiError(response.status);
      return response.json();
    },
    catch: (error) => error as ApiError,
  });

// Retry up to 3 times with 500ms between attempts
const fetchWithRetry = (userId: string) =>
  pipe(
    fetchUserData(userId),
    Effect.retry(
      Schedule.recurs(3).pipe(Schedule.addDelay(() => "500 millis"))
    ),
    Effect.catchAll((error) =>
      Effect.succeed({ error: `Failed after retries: ${error._tag}` })
    )
  );

Rationale:

Use Effect.retry to automatically retry an Effect that fails. Combine it with a Schedule to control how many times to retry and how long to wait between attempts.

Network requests fail. Databases time out. Services go down temporarily. Instead of failing immediately, you often want to retry a few times. Effect makes this a one-liner.

---

Hello World: Your First Effect

Rule: Create your first Effect program with Effect.succeed.

Good Example:

import { Effect } from "effect";

// Step 1: Create an Effect that succeeds with a value
const helloWorld = Effect.succeed("Hello, Effect!");

// Step 2: Run the Effect and get the result
const result = Effect.runSync(helloWorld);

console.log(result); // "Hello, Effect!"

Rationale:

Create your first Effect using Effect.succeed to wrap a value, then run it with Effect.runSync to see the result.