Examples

Input Validation

Email Validation

import { check } from "resafe";

// ✅ Safe email pattern
const safeEmail = "^[\\w._%+-]+@[\\w.-]+\\.[A-Za-z]{2,}$";
const r1 = check(safeEmail, { silent: true });
console.log(r1.safe);  // true

// ❌ Dangerous email pattern
const dangerousEmail = "^(.+)*@(.+)*\\.(com|org)$";
const r2 = check(dangerousEmail, { silent: true });
console.log(r2.safe);    // false
console.log(r2.radius);  // > 1.0

// ✅ Fixed version
const fixedEmail = "^.+@.+\\.(com|org)$";
check(fixedEmail);  // Safe

Web Security

XSS Prevention

// ✅ Safe script tag detection
const safeScript = "<script[^>]*>";
check(safeScript);  // Safe

// ❌ Dangerous script detection
const dangerousScript = "(.*<script.*>)*";
check(dangerousScript);  // Unsafe

// ✅ Fixed version
const fixedScript = ".*<script.*>";
check(fixedScript);  // Safe

Production Middleware

Express.js Middleware

import express from "express";
import { check } from "resafe";

const app = express();

app.use("/api/search", (req, res, next) => {
  const { pattern } = req.query;
  
  if (typeof pattern === "string") {
    try {
      check(pattern, { 
        throwErr: true, 
        silent: true,
        threshold: 1.0
      });
      next();
    } catch (error) {
      res.status(400).json({ 
        error: "Unsafe regex pattern detected",
        message: error.message 
      });
    }
  } else {
    next();
  }
});

Fastify Plugin

import fastify from "fastify";
import { check } from "resafe";

const server = fastify();

server.addHook("preHandler", async (request, reply) => {
  const pattern = request.query.pattern;
  
  if (typeof pattern === "string") {
    const result = check(pattern, { silent: true });
    
    if (!result.safe) {
      reply.code(400).send({
        error: "Unsafe regex pattern",
        radius: result.radius
      });
    }
  }
});