apamate-validator v0.0.8

Chained validation rules

Facilitates the validation of strings by chaining series of rules.

Translations

• Spanish

Release Notes 0.0.7

• Added predefined rules.

Installation

npm i chained-validation-rules

Starting

My first validator

import { Validator } from 'chained-validation-rules';

// Instantiating a new validator
const validator = new Validator();

// First rule, it will only be approved if the string to evaluate contains some character, otherwise it will show the 
// message "The text is required"
validator.rule('The text is required', evaluate => {
  return !!evaluate;
});

// Second rule, it will only be approved if the string to be evaluated is equal to "xxx", otherwise it will show the
// message "The text is different from xxx"
validator.rule('The text is different from xxx', evaluate => {
  return evaluate === 'xxx';
})

The validator rule function allows you to create specific validation rules, associated with an error message in case that this validation is not fulfilled.

Note:

• An indeterminate number of rules can be added.
• Rules will be evaluated in the order in which they were added.
• When a rule fails, the rest are ignored.
• A string is considered valid only if it passes all the rules.

Simplifying code

You can create a Validator instance using the pattern builder with .ValidatorBuilder().

import { ValidatorBuilder } from 'chained-validation-rules';

const validator = new ValidatorBuilder()
  .rule('The text is required', evaluate => !!evaluate)
  .rule('The text is different from xxx', evaluate => evaluate === 'xxx')
  .build();

Predefined rules

Validator offers a series of predefined rules, trying to cover the most common validation cases.

Predefined rules can simplify the definition of a Validator.

import { ValidatorBuilder } from 'chained-validation-rules';

const validator = new ValidatorBuilder()
        .required('Required')
        .minLength(6, 'At least 6 characters required')
        .build();

Default messages

The messages in the predefined rules are optional, so you can simplify the implementations as follows.

import { ValidatorBuilder } from "chained-validation-rules";

const validator = new ValidatorBuilder()
        .required()
        .minLength(6)
        .build();

The default messages are found in the messagesEn objects for English messages, and in messagesEs for Spanish messages, both implement the Messages interface.

Note:

• The %s will be replaced by the condition passed in the predefined rule.

Change default messages

Validator has a static variable called .messages which receives an object of type Messages as a parameter.

import { Validator } from 'chained-validation-rules';

Validator.messages = {
  compareMessage: 'Custom message',
  requiredMessage: 'Custom message',
  minLengthMessage: 'Custom message',
  maxLengthMessage: 'Custom message',
  textLengthMessage: 'Custom message',
  emailMessage: 'Custom message',
  reMessage: 'Custom message'
}

Changing the message language

import { Validator, messagesEs } from 'chained-validation-rules';

Validator.messages = messagesEs

Validating a string

Working with events

The .isValid method is used to find out if the string is valid.

import { ValidatorBuilder } from 'chained-validation-rules';

const validator = new ValidatorBuilder()
  .rule('The text is different from xxx', evaluate => evaluate === 'xxx')
  .build();

function submit() {
  validator.isValid('yyy'); // false
  validator.isValid('xxx'); // true
}

In case you want to compare two strings, which is very useful to validate passwords, you can use the method .isMath. Optionally, an error message can be defined by defining the .notMatchMessage property for the error message if it doesn't match.

import { ValidatorBuilder } from 'chained-validation-rules';

const validator = new ValidatorBuilder()
  .rule('The text is different from xxx', evaluate => evaluate === 'xxx')
  .setNotMatchMessage('Not match')
  .build();

function submit() {
  validator.isMatch('abc', 'xyz'); // false
  validator.isMatch('abc', 'abc'); // true
}

The .onInvalidEvaluation event is executed when a rule fails when it is evaluated and returns the error message associated.

import { ValidatorBuilder } from 'chained-validation-rules';

const validator = new ValidatorBuilder()
  .rule('The text is different from xxx', evaluate => evaluate === 'xxx')
  .addOnInvalidEvaluation( (message: string) => console.log(message) ) // It is only executed if the validation of some rule fails
  .build();

function submit() {
  validator.isValid('yyy');
}

Work with exceptions

If you prefer not to use the .onInvalidEvaluation event, you can use the .validOrFail and .compareOrFail methods replacing the .isValid and .isMatch methods respectively.

The main difference is that these methods do not return any value and if they fail, they throw an exception to the type InvalidEvaluationError containing the error message from the rule along with the value of the string to be evaluated.

import { ValidatorBuilder, InvalidEvaluationError } from 'chained-validation-rules';

const validator = new ValidatorBuilder()
  .rule('The text is different from xxx', evaluate => evaluate === 'xxx')
  .build();

function submit() {
  try {
    validator.validOrFail()('yyy');
    validator.compareOrFail('xxx', 'yyy');
    // TODO
  } catch (e) {
    if (e instanceof InvalidEvaluationError) {
      console.log(`value: ${e.value}, error message: ${e.message}`)
    }
  }
}

recommendations

Commonly, there are several instances of strings to which to apply the same validation rules. for these cases it is recommended to define Validators per context, in order to define our Validator once and reuse it. This logic is possible, since Validator includes a .copy method which generates copies of it.

validators.ts

import { ValidatorBuilder } from 'chained-validation-rules';

export const email = new ValidatorBuilder()
  .required()
  .email()
  .build();

export const password = new ValidatorBuilder()
  .minLength(8)
  .build();

login.ts

import { ValidatorBuilder, InvalidEvaluationError } from 'chained-validation-rules';
import { email, password } from './validators.ts';

const emailValidator = email.copy();
const pswValidator = password.copy()

let email, psw, pswConfirmation: string = '';

function submit() {
  if (
    !emailValidator.isValid(email) ||
    !pswValidator.isMatch(psw, pswConfirmation)
  ) return;
  // TODO
}

function submitWithExceptions() {
  try {
    emailValidator.validOrFail(email);
    pswValidator.compareOrFail(psw, pswConfirmation);
    // TODO
  } catch (e) {
    if (e instanceof InvalidEvaluationError) {
      console.log(`valor: ${e.value}, mensaje de error: ${e.message}`)
    }
  }
}