How can I implement async validation in TypeScript using class-validator?

How can I implement async validation in TypeScript using class-validator?

You can use the @Validate decorator along with a custom validation function that returns a Promise. This allows you to perform asynchronous checks.

Can you show me a code example of that?

Sure! Here's a simple example:

import { IsEmail, validate } from 'class-validator';

class User {
    @IsEmail()
    email: string;

    @Validate(IsUniqueEmail)
    async uniqueEmail: string;
}

async function IsUniqueEmail(email: string) {
    const existingUser = await findUserByEmail(email);
    return !existingUser;
}

This checks if the email is unique asynchronously.

What if I want to validate multiple fields asynchronously?

You can create multiple custom validators and use them on different fields. Each validator can handle its own async logic.