CodeSampleX

Sample

express-rate-limit 8.6.1

Verified sample for npm express-rate-limit 8.6.1. The contract ran on node 22 · linux alpine/x64 · docker and passed: rateLimit creates a middleware function…

sha256:1b311fd97d14f054f950e4bc8575fef2f585e1e800babd49e4e67ce59deb6e13

This network offers one thing: a sample that builds. It ran the sample in a sandbox and kept the signed receipt. It grades nothing and warrants nothing — whether the same code builds where you are is not something it measured. How many distinct signing keys filed a passing contract receipt. One is the author alone; more than one means somebody else built it too. A key is self-generated with nothing registered behind it, so it counts keys, not people. MIT-0

Execution evidence

The declared environment and the signed runs are kept apart, so you can see exactly what this sample ran and where.

Evidence basis
Signed contract pass
Verification receipts
1
Signing keys that built it
1
Declared environment node 22.23 linux 24 · ubuntu · glibc 2.39 x64 node 22.23 javascript npm 10

Verification-run environments

Environment Contract Stages Run
node 22 · linux alpine/x64 · docker ed25519:c1973797be207ac4 PASS compile:SKIPPED · contract:PASS · load:PASS · resolve:PASS
CONTAINER_RUN · node-typescript@1node:22-alpine@sha256:c610fcdfb1d5…		 2026-08-27

Case

HOW
Goal
verify pkg:npm/express-rate-limit@8.6.1
Packages
Environment
node 22.23.2
Created
2026-08-27T16:55:30Z

Contract

  1. rateLimit creates a middleware function with resetKey and getKey methods
  2. rateLimit allows requests within limit and attaches rateLimit metadata to request object
  3. rateLimit returns HTTP 429 and default message when limit is exceeded
  4. rateLimit sets standard RateLimit and legacy X-RateLimit headers when configured
  5. rateLimit supports custom keyGenerator and skip conditions
  6. MemoryStore tracks hit counts and supports increment, decrement, get, resetKey, and resetAll
  7. ipKeyGenerator generates normalized keys for IPv4 and IPv6 addresses

Files

  • PROMPT.md
  • csx.json
  • package-lock.json
  • package.json
  • spec.json
  • src/index.mjs
  • test/contract.mjs

Download the source artifact (tar.gz)

Source

PROMPT.md
Clean-room public code sample — generation instructions

Write a brand-new, minimal, self-contained code sample in this clean-room directory.
Do not copy, paraphrase, or reference any existing project source. Work only from this spec.

A csx.json manifest scaffold already exists. Do not recreate it from memory. Preserve its case.goal, packages and symbols; fill its empty case.contract with exact assertions and correct its environment, commands and verifierAdapter for the files you generate.

Goal: verify pkg:npm/express-rate-limit@8.6.1
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:npm/express-rate-limit@8.6.1
Constraints:
  - executionContext: node
Required runtime conditions:
  - ecosystem: npm
  - language: javascript
  - moduleSystem: cjs
  - packageManager: npm@10.9.8
  - runtime: node@22.23.2

Rules:
  - One focused purpose; the smallest project that proves the goal.
  - Include a contract test (test/contract.*) that runs OFFLINE and exits 0 exactly when the goal behavior works.
  - Pin every dependency with a lockfile so resolution is reproducible.
  - No secrets, credentials, or tokens. No real URLs (only example.com or localhost). No absolute paths.
  - No personal names, emails, company names, or project identifiers of any kind.
  - No binaries and no generated output (node_modules, dist, target, venv, .git, .env).
  - Keep it under 200 files and 256KB packed.
csx.json
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package.json
{
  "name": "sample-express-rate-limit",
  "version": "1.0.0",
  "private": true,
  "type": "module",
  "license": "MIT-0",
  "dependencies": {
    "express-rate-limit": "8.6.1"
  }
}
spec.json
{
  "schemaVersion": 1,
  "goal": "verify pkg:npm/express-rate-limit@8.6.1",
  "kind": "HOW",
  "packages": [
    "pkg:npm/express-rate-limit@8.6.1"
  ],
  "constraints": {
    "executionContext": "node"
  },
  "runtimeConditions": {
    "ecosystem": "npm",
    "language": "javascript",
    "moduleSystem": "cjs",
    "packageManager": "npm@10.9.8",
    "runtime": "node@22.23.2"
  }
}
src/index.mjs
import { rateLimit, MemoryStore, ipKeyGenerator } from "express-rate-limit";

export function createLimiter(options = {}) {
  return rateLimit({
    validate: false,
    ...options,
  });
}

export function createIpLimiter(limit = 5, windowMs = 60000) {
  return rateLimit({
    limit,
    windowMs,
    standardHeaders: "draft-7",
    legacyHeaders: true,
    validate: false,
  });
}

export function createCustomKeyLimiter(keyGenerator, limit = 5, windowMs = 60000) {
  return rateLimit({
    keyGenerator,
    limit,
    windowMs,
    validate: false,
  });
}

export function createMemoryStore(windowMs = 60000) {
  const store = new MemoryStore();
  store.init({ windowMs });
  return store;
}

export function normalizeIp(ip, ipv6Subnet) {
  return ipKeyGenerator(ip, ipv6Subnet);
}

export { rateLimit, MemoryStore, ipKeyGenerator };
test/contract.mjs
import assert from "node:assert/strict";
import {
  createLimiter,
  createIpLimiter,
  createCustomKeyLimiter,
  createMemoryStore,
  normalizeIp,
  rateLimit,
  MemoryStore,
  ipKeyGenerator
} from "../src/index.mjs";

function createMockReq(options = {}) {
  return {
    ip: options.ip || "127.0.0.1",
    path: options.path || "/",
    headers: options.headers || {},
    get(name) {
      return this.headers[name.toLowerCase()] || "";
    },
    ...options
  };
}

function createMockRes() {
  return {
    statusCode: 200,
    headers: {},
    body: undefined,
    ended: false,
    setHeader(name, value) {
      this.headers[name.toLowerCase()] = String(value);
      return this;
    },
    getHeader(name) {
      return this.headers[name.toLowerCase()];
    },
    status(code) {
      this.statusCode = code;
      return this;
    },
    send(body) {
      this.body = body;
      this.ended = true;
      return this;
    }
  };
}

function runMiddleware(middleware, req, res) {
  return new Promise((resolve) => {
    let nextCalled = false;
    const next = (err) => {
      nextCalled = true;
      resolve({ nextCalled, err });
    };
    Promise.resolve(middleware(req, res, next)).then(() => {
      if (!nextCalled && res.ended) {
        resolve({ nextCalled: false });
      }
    });
  });
}

// Test 1: rateLimit creates a middleware function with resetKey and getKey methods
{
  const limiter = createLimiter({ limit: 10 });
  assert.equal(typeof limiter, "function");
  assert.equal(typeof limiter.resetKey, "function");
  assert.equal(typeof limiter.getKey, "function");
}

// Test 2: rateLimit allows requests within limit and attaches rateLimit metadata to request object
{
  const limiter = createLimiter({ limit: 3, windowMs: 60000 });
  const req = createMockReq({ ip: "192.168.1.10" });
  const res = createMockRes();

  const result = await runMiddleware(limiter, req, res);
  assert.equal(result.nextCalled, true);
  assert.equal(res.statusCode, 200);
  assert.ok(req.rateLimit, "req.rateLimit should be defined");
  assert.equal(req.rateLimit.limit, 3);
  assert.equal(req.rateLimit.used, 1);
  assert.equal(req.rateLimit.remaining, 2);
  assert.ok(req.rateLimit.resetTime instanceof Date);
}

// Test 3: rateLimit returns HTTP 429 and default message when limit is exceeded
{
  const limiter = createLimiter({ limit: 2, windowMs: 60000 });
  const clientIp = "192.168.1.20";

  // Request 1
  const req1 = createMockReq({ ip: clientIp });
  const res1 = createMockRes();
  const res1Status = await runMiddleware(limiter, req1, res1);
  assert.equal(res1Status.nextCalled, true);

  // Request 2
  const req2 = createMockReq({ ip: clientIp });
  const res2 = createMockRes();
  const res2Status = await runMiddleware(limiter, req2, res2);
  assert.equal(res2Status.nextCalled, true);

  // Request 3 - should exceed limit
  const req3 = createMockReq({ ip: clientIp });
  const res3 = createMockRes();
  const res3Status = await runMiddleware(limiter, req3, res3);
  assert.equal(res3Status.nextCalled, false);
  assert.equal(res3.statusCode, 429);
  assert.equal(res3.body, "Too many requests, please try again later.");
}

// Test 4: rateLimit sets standard RateLimit and legacy X-RateLimit headers when configured
{
  const limiter = createIpLimiter(5, 60000);
  const req = createMockReq({ ip: "192.168.1.30" });
  const res = createMockRes();

  const result = await runMiddleware(limiter, req, res);
  assert.equal(result.nextCalled, true);
  assert.equal(res.getHeader("x-ratelimit-limit"), "5");
  assert.equal(res.getHeader("x-ratelimit-remaining"), "4");
  assert.ok(res.getHeader("x-ratelimit-reset") !== undefined);
  assert.ok(res.getHeader("ratelimit-policy") !== undefined || res.getHeader("ratelimit") !== undefined || res.getHeader("ratelimit-limit") !== undefined);
}

// Test 5: rateLimit supports custom keyGenerator and skip conditions
{
  const customLimiter = createCustomKeyLimiter(
    (req) => req.headers["x-api-key"] || req.ip,
    2,
    60000
  );

  const reqA1 = createMockReq({ ip: "10.0.0.1", headers: { "x-api-key": "key-alpha" } });
  const resA1 = createMockRes();
  await runMiddleware(customLimiter, reqA1, resA1);

  const reqA2 = createMockReq({ ip: "10.0.0.2", headers: { "x-api-key": "key-alpha" } });
  const resA2 = createMockRes();
  await runMiddleware(customLimiter, reqA2, resA2);

  // 3rd request with same api key but different IP -> blocked
  const reqA3 = createMockReq({ ip: "10.0.0.3", headers: { "x-api-key": "key-alpha" } });
  const resA3 = createMockRes();
  const resA3Result = await runMiddleware(customLimiter, reqA3, resA3);
  assert.equal(resA3Result.nextCalled, false);
  assert.equal(resA3.statusCode, 429);

  // Different API key -> allowed
  const reqB1 = createMockReq({ ip: "10.0.0.1", headers: { "x-api-key": "key-beta" } });
  const resB1 = createMockRes();
  const resB1Result = await runMiddleware(customLimiter, reqB1, resB1);
  assert.equal(resB1Result.nextCalled, true);
}

// Test 6: MemoryStore tracks hit counts and supports increment, decrement, get, resetKey, and resetAll
{
  const store = createMemoryStore(60000);

  const inc1 = await store.increment("client-1");
  assert.equal(inc1.totalHits, 1);
  assert.ok(inc1.resetTime instanceof Date);

  const inc2 = await store.increment("client-1");
  assert.equal(inc2.totalHits, 2);

  const got = await store.get("client-1");
  assert.equal(got.totalHits, 2);

  await store.decrement("client-1");
  const afterDec = await store.get("client-1");
  assert.equal(afterDec.totalHits, 1);

  await store.resetKey("client-1");
  const afterReset = await store.get("client-1");
  assert.equal(afterReset, undefined);

  await store.increment("client-2");
  await store.resetAll();
  const afterResetAll = await store.get("client-2");
  assert.equal(afterResetAll, undefined);

  store.shutdown();
}

// Test 7: ipKeyGenerator generates normalized keys for IPv4 and IPv6 addresses
{
  const ipv4Key = normalizeIp("192.168.1.1");
  assert.equal(ipv4Key, "192.168.1.1");

  const ipv6Key = normalizeIp("2001:0db8:85a3:0000:0000:8a2e:0370:7334", 64);
  assert.ok(typeof ipv6Key === "string");
  assert.ok(ipv6Key.length > 0);
}

console.log("All pkg:npm/express-rate-limit@8.6.1 contract tests passed successfully.");

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