docs(examples): Added Node.js Express server example (#333)

- New example app showing usage of Arcjet with [Express](https://expressjs.com/).
- Added note to READMEs about the availability of `--env-file`

.github/dependabot.yml

@@ -221,7 +221,24 @@ updates:
         versions: [">18.18"]
 
   - package-ecosystem: npm
-    directory: /examples/node-rl
+    directory: /examples/nodejs-express-rl
+    schedule:
+      # Our dependencies should be checked daily
+      interval: daily
+    assignees:
+      - blaine-arcjet
+    reviewers:
+      - blaine-arcjet
+    commit-message:
+      prefix: deps(example)
+      prefix-development: deps(example)
+    groups:
+      dependencies:
+        patterns:
+          - "*"
+
+  - package-ecosystem: npm
+    directory: /examples/nodejs-rl
     schedule:
       # Our dependencies should be checked daily
       interval: daily
@@ -236,8 +253,3 @@ updates:
       dependencies:
         patterns:
           - "*"
-    ignore:
-      # Ignore updates to the @types/node package due to conflict between
-      # Headers in DOM.
-      - dependency-name: "@types/node"
-        versions: [">18.18"]

examples/nodejs-express-rl/.env.local.example

@@ -0,0 +1 @@
+ARCJET_KEY=

examples/nodejs-express-rl/README.md

@@ -0,0 +1,42 @@
+<a href="https://arcjet.com" target="_arcjet-home">
+  <picture>
+    <source media="(prefers-color-scheme: dark)" srcset="https://arcjet.com/arcjet-logo-minimal-dark-mark-all.svg">
+    <img src="https://arcjet.com/arcjet-logo-minimal-light-mark-all.svg" alt="Arcjet Logo" height="128" width="auto">
+  </picture>
+</a>
+
+# Arcjet Rate Limit with Express for Node.js
+
+This example shows how to use Arcjet with a Node.js
+[Express](https://expressjs.com/) server.
+
+## How to use
+
+1. From the root of the project, install the SDK dependencies.
+
+   ```bash
+   npm ci
+   ```
+
+2. Enter this directory and install the example's dependencies.
+
+   ```bash
+   cd examples/nodejs-express
+   npm ci
+   ```
+
+3. Rename `.env.local.example` to `.env.local` and add your Arcjet key.
+
+4. Start the server.
+
+   ```bash
+   npm start
+   ```
+
+   This assumes you're using Node.js 20 or later because the `start` script
+   loads a local environment file with `--env-file`. If you're using an older
+   version of Node.js, you can use a package like
+   [dotenv](https://www.npmjs.com/package/dotenv) to load the environment file.
+
+5. Visit `http://localhost:3000/`.
+6. Refresh the page to trigger the rate limit.

examples/nodejs-express-rl/index.js

@@ -0,0 +1,38 @@
+import arcjet, { fixedWindow } from "@arcjet/node";
+import express from "express";
+
+const app = express();
+const port = 3000;
+
+const aj = arcjet({
+  // Get your site key from https://app.arcjet.com and set it as an environment
+  // variable rather than hard coding.
+  key: process.env.ARCJET_KEY,
+  rules: [
+    // Fixed window rate limit. Arcjet also supports sliding window and token
+    // bucket.
+    fixedWindow({
+      mode: "LIVE", // will block requests. Use "DRY_RUN" to log only
+      // Limiting by ip.src is the default if not specified
+      //characteristics: ["ip.src"],
+      window: "1m", // 1 min fixed window
+      max: 1, // allow a single request (for demo purposes)
+    }),
+  ],
+});
+
+app.get('/', async (req, res) => {
+  const decision = await aj.protect(req);
+
+  if (decision.isDenied()) {
+    res.writeHead(429, { "Content-Type": "application/json" });
+    res.end(JSON.stringify({ error: "Too Many Requests" }));
+  } else {
+    res.writeHead(200, { "Content-Type": "application/json" });
+    res.end(JSON.stringify({ message: "Hello World" }));
+  }
+})
+
+app.listen(port, () => {
+  console.log(`Example app listening on port ${port}`)
+})