📦 captcha-canvas-js

A lightweight, framework-independent image captcha generator for Node.js — supports base64 output, in-memory or custom storage, and easy integration with Express, NestJS, Koa, etc.

✨ Features

• ✅ Generate random text-based image captchas (PNG)
• ✅ Supports Base64 image output
• ✅ Pluggable storage (in-memory, Redis, etc.)
• ✅ Fully written in TypeScript
• ✅ Framework-agnostic: works with Express, NestJS, Koa, etc.
• ✅ Includes CAPTCHA verification method

📦 Installation

npm install 

or

pnpm add captcha-canvas-js

🧱 Usage Example (Basic)

import { Captcha, MemoryStore } from "captcha-canvas-js";

const captcha = new Captcha(new MemoryStore());

const { id, imageBase64, text } = await captcha.generate();

console.log("Captcha ID:", id);
console.log("Captcha Text:", text); // You may skip logging this in production
console.log("Image (base64):", imageBase64);

// Later verify:
const isValid = await captcha.verify(id, "user-input");

🧩 API

new Captcha(store: CaptchaStore, options?: CaptchaOptions)

• store: storage object (e.g., MemoryStore, or your own)
• options: optional customization:

{
  width?: number;         // default: 120
  height?: number;        // default: 40
  length?: number;        // number of characters (default: 4)
  fontSize?: number;      // default: 28
  charset?: string;       // default: A-Z + 2-9 (excluding O, I, 1)
  background?: string;    // e.g., "#f7f7f7"
  noise?: number;         // number of random lines (default: 3)
}

await captcha.generate(): Promise<CaptchaResult>

Returns:

{
  id: string;
  text: string;
  imageBase64: string; // starts with "data:image/png;base64,..."
}

await captcha.verify(id: string, input: string): Promise<boolean>

Checks if the user input matches the stored captcha text.

🗃 Storage

✅ Built-in: MemoryStore

In-memory temporary store (auto-expire in 3 minutes by default).

✅ Custom Store Interface

You can implement your own CaptchaStore (e.g., Redis):

export interface CaptchaStore {
  set(id: string, value: string): Promise<void>;
  get(id: string): Promise<string | null>;
  delete(id: string): Promise<void>;
}

🔒 Security Notes

• Avoid exposing text in production
• Always expire stored captchas (e.g., 3–5 minutes)
• Rate limit captcha generation per IP/user if needed

🧪 Development

# build for ESM and CommonJS
npm run build

📄 License

MIT

notice

• The published package may have errors
• We will continue to update

❤️ Author

Created by alias-- yiqishuyuan