How can I create custom validation rules using async-validator?

How can I create custom validation rules using async-validator?

You can create custom validation rules in async-validator by defining a rule object with a validator function. Would you like an example?

Yes, please provide an example of a custom rule.

Sure! Here's a simple example:

const validator = new AsyncValidator({
  username: [{
    validator: (rule, value, callback) => {
      if (value && value.length < 5) {
        callback('Username must be at least 5 characters long.');
      } else {
        callback();
      }
    },
    trigger: 'blur'
  }]
});

This rule checks if the username is at least 5 characters long.

How do I use this custom rule in my form validation?

You can use the custom rule by passing it to the validate method of your form. For example:

validator.validate({ username: 'test' }, (errors) => {
  if (errors) {
    console.log(errors);
  } else {
    console.log('Validation passed!');
  }
});