Clone an array
Create a new array without copying the objects inside it.
function clone(values) { return [...values]; }arrayA new edition of 1loc.dev
Small code.
Working integrations.
Useful JavaScript. Practical email recipes.Run the code. Read the edge case.Take a working example back to your project.
What are you building?
Start with the problem in front of you.
01 — The library
Find your next small solution.
Small enough to read in one breath — with the edge case and the limits written down.
Remove duplicate values
Keep the first occurrence of each value, in its original order.
function unique(values) { return [...new Set(values)]; }arrayFlatten a nested array
Turn a nested array into one sequence of values.
function flatten(values) { return values.flat(Infinity); }arraySplit an array into chunks
Build consecutive chunks without changing the original array.
function chunk({ values, size }) { return Array.from({ length: Math.ceil(values.length / size) …arrayFind the intersection of arrays
Return the distinct values that occur in both arrays.
function intersection({ left, right }) { const other = new Set(right); return [...new Set(left)…arraySort numbers in ascending order
Sort a numeric copy instead of using JavaScript’s default string ordering.
function sortNumbers(values) { return [...values].sort((a, b) => a - b); }arrayPrefer it all on one page? Print the one-line sheet — every utility as the code that runs.
02 — Recipes
From one line to a working integration.
Complete Node.js/TypeScript starters with tests, failure handling and a local mock. No account is needed to run them.
- R01 · Email · Node.js · RetriesLocal mock
Send your first transactional email
Build one server-side request, keep its idempotency key across retries, and start with a local mock.
10 files · Node.js 22.23.2 / TypeScript - R02 · Email · Idempotency · SQLiteLocal mock
Confirm an order without a duplicate retry
Persist the business event before the request and reuse its provider key after recoverable failures.
12 files · Node.js 22.23.2 / TypeScript - R03 · Email · Templates · Node.jsLocal mock
Send a welcome email from a pinned template
Create a draft, publish an explicit version, and send data against that immutable version.
11 files · Node.js 22.23.2 / TypeScript - R04 · Webhooks · Security · SQLiteLocal mock
Track recipient delivery with a signed webhook
Authenticate raw bytes, reject stale signatures, and persist independent state for each recipient.
12 files · Node.js 22.23.2 / TypeScript - R05 · Validation · Domains · Node.jsLocal mock
Check disposable domains during sign-up
Ask about a domain without sending a full address, and keep unavailable results explicitly unknown.
9 files · Node.js 22.23.2 / TypeScript - Builder · 7 combinationsDeterministic
Build your own starter
Pick a task and an environment. Get the complete files, prerequisites and a context package for your agent.
Open the recipe builder →
03 — Labs
See what the code does.
Change the data, follow the states and break a signature on purpose. Everything runs in your browser.
Input → Code → Output
Run a function from a closed registry of curated utilities. Edit JSON, try edge cases and inspect actual output.
Recipe builder
Choose a supported task and environment. Get complete files, prerequisites, tests and a context package.
Delivery & retries
Step through API acceptance, an uncertain response, a retry and a duplicate avoided.
Webhook signatures
Sign a synthetic delivery event, then watch a re-serialized body, a tampered byte or a late replay fail verification.
04 — Maintained by Oveyon
When the next line is an email.
1loc.dev is maintained by Oveyon: transactional email infrastructure with an API and SMTP for your software, inboxes your agents can read safely, and a record of every send. The recipes here are written against its API.
curl https://api.oveyon.com/v1/send \
-H "Authorization: Bearer $OVEYON_API_KEY" \
-H 'Content-Type: application/json' \
-H 'X-Oveyon-Sandbox: 1' \
-H 'Idempotency-Key: 1loc:welcome:demo-001' \
--data '{"from":"sender@your-verified-domain.example","to":"reader@example.net","subject":"Demo","text":"Synthetic sandbox example"}'
SendOne request, one outcome per recipient
Reuse an
Idempotency-Keyand a retry inside 24 hours returns the original message instead of a second one.ReceiveMail arrives with a verdict
Inbound messages are evaluated before an agent reads them; a dangerous one waits for a person to release it.
ProveSigned, per-recipient events
Every webhook carries
sha256=HMAC(timestamp.body). Break one in the lab.
Free plan: 1,000 emails a month, no card required — as published on oveyon.com, checked October 28, 2026. Oveyon maintains this site; the relationship is commercial and disclosed.
05 — How we verify
Code with a paper trail.
Each utility links to its original source. Each recipe names its runtime, expected result and limits. A local mock is labeled as a local mock.
Local fixtures Executed
Transformations, request construction, signatures, persistence and state transitions run against synthetic data.
Contract review Reviewed
Examples checked against a captured Oveyon OpenAPI 3.1 document and the official reference.
Authenticated sandbox Not executed
Requires a test account and a manual job. No badge is shown until it runs.
Controlled real delivery Not executed
Even then, recipient-server acceptance would not prove inbox placement.
Changelog · October 28, 2026
The whole original collection is back.
Every page of the original 1loc collection by Nguyen Huu Phuoc and contributors lives again at its address: 235 run in the local lab, 78 more as references whose usage runs in Node.js and Chromium. Bugs found in review are fixed and explained on each page.
Read the changelog