Express Integration

Block disposable emails in your Express app with a simple middleware or inline check.

Inline check

The quickest way — add a check directly in your route handler:

server.tstypescript

import express from 'express';
import { isDisposable } from '@isdisposable/js';

const app = express();
app.use(express.json());

app.post('/signup', (req, res) => {
  const { email } = req.body;

  if (isDisposable(email)) {
    return res.status(400).json({
      error: 'Please use a real email address.'
    });
  }

  // Continue with signup...
  res.json({ success: true });
});

app.listen(3000);

Reusable middleware

Create a middleware you can apply to any route that accepts emails:

middleware/block-disposable.tstypescript

import { isDisposable } from '@isdisposable/js';
import { Request, Response, NextFunction } from 'express';

interface Options {
  emailField?: string;    // which field in req.body (default: 'email')
  errorMessage?: string;  // custom error message
  errorStatus?: number;   // HTTP status code (default: 400)
}

export function blockDisposable(options: Options = {}) {
  const {
    emailField = 'email',
    errorMessage = 'Please use a real email address.',
    errorStatus = 400,
  } = options;

  return (req: Request, res: Response, next: NextFunction) => {
    const email = req.body?.[emailField];

    if (!email) return next();

    if (isDisposable(email)) {
      return res.status(errorStatus).json({ error: errorMessage });
    }

    next();
  };
}

server.tstypescript

import express from 'express';
import { blockDisposable } from './middleware/block-disposable';

const app = express();
app.use(express.json());

// Apply to specific routes
app.post('/signup', blockDisposable(), (req, res) => {
  res.json({ success: true });
});

app.post('/invite', blockDisposable({ emailField: 'inviteeEmail' }), (req, res) => {
  res.json({ invited: true });
});

// Or apply globally to all POST routes
// app.use(blockDisposable());

With Pro API

For real-time detection with risk scoring:

server.tstypescript

import express from 'express';
import { createIsDisposable } from '@isdisposable/js';

const checker = createIsDisposable({
  apiKey: process.env.ISDISPOSABLE_API_KEY!,
});

const app = express();
app.use(express.json());

app.post('/signup', async (req, res) => {
  const { email } = req.body;

  const result = await checker.check(email);

  if (result.disposable) {
    return res.status(400).json({
      error: 'Please use a real email address.',
      score: result.score,
      reason: result.reason,
    });
  }

  // result.score < 50 — safe to proceed
  res.json({ success: true });
});

Score threshold

By default, emails with a score of 50 or higher are considered disposable. You can use a custom threshold — for example, only block emails with score >= 70 for a stricter filter.

Fastify

Works the same way in Fastify:

server.tstypescript

import Fastify from 'fastify';
import { isDisposable } from '@isdisposable/js';

const app = Fastify();

app.post('/signup', async (request, reply) => {
  const { email } = request.body as { email: string };

  if (isDisposable(email)) {
    return reply.status(400).send({
      error: 'Please use a real email address.'
    });
  }

  return { success: true };
});