How to validate and sanitize input data in Next.js API routes?

To validate and sanitize input data in Next.js API routes, you can use libraries like Joi, Yup, or validator.js. These libraries help ensure that the data received from clients meets the expected format and is safe to use.

Example using Joi:

// app/api/users/route.js
import Joi from "joi";

const userSchema = Joi.object({
  name: Joi.string().min(3).max(30).required(),
  email: Joi.string().email().required(),
  age: Joi.number().integer().min(0).optional(),
});

export async function POST(request) {
  const data = await request.json();

  // Validate input data
  const { error, value } = userSchema.validate(data);
  if (error) {
    return new Response(
      JSON.stringify({ error: error.details[0].message }),
      {
        status: 400,
        headers: { "Content-Type": "application/json" },
      }
    );
  }

  // Proceed with sanitized data
  const user = await createUser(value);
  return new Response(JSON.stringify(user), {
    status: 201,
    headers: { "Content-Type": "application/json" },
  });
}

In this example, the userSchema defines the expected structure of the input data. The POST function validates the incoming data against this schema and returns an error response if validation fails.