favalid

Validator Framework for javascript.

Getting Started

Prerequisites

• Node.js v8+
• npm or yarn

Installing

$ npm install favalid

Usage

Primitive Validator

1. Write higher order validator using tester(). tester() takes two arguments. first argument is (value: any) => bool function, which represent validation rules. Second argument is () => string function, which represents validation error message.

import { tester } from 'favalid';

const validator = tester((targetValue) => {
  return targetValue < 100;
}, () => {
  return 'must be less than 100';
})

2. Use it! tester() returns simple validator function, (value: any) => ({error: bool, message: string}).

console.log(validator(99)); // => { error: false, message: '' }
console.log(validator(101)); // => { error: true, message: 'must ne less than 100' }

Combined Validator

1. You can combine these validators using combine(...validators). combine() returns also validator.

import { tester, combine } from 'favalid';
const validator1 = tester((targetValue) => {
  return targetValue < 100;
}, () => {
  return 'must be less than 100';
})

const validator2 = tester((targetValue) => {
  return targetValue > 20;
}, () => {
  return 'must be higher than 20';
})

const combinedValidator = combine(validator1, validator2)

2. Use it.

console.log(combinedValidator(80)) // { error: false, message: '' }

console.log(combinedValidator(101)) // { error: true, message: 'must be less than 100' }

console.log(combinedValidator(19)) // { error: true, message: 'must be higher than 20' }

If target values are failed multiple tests, combined validator returns first failed message.

import { tester, combine } from 'favalid';
const minLength = tester((targetValue) => {
  return [...targetValue].length > 2;
}, () => {
  return 'too few letters';
})

const regex = tester((targetValue) => {
  return /^[a-zA-Z]+$/.test(targetValue) // only contains alphabet letters.
}, () => {
  return 'invalid format';
})

const combinedValidator = combine(minLength, regex)

console.log(combinedValidator('a')) // { error: true, message: 'too few letters' }

console.log(combinedValidator('1')) // { error: true, message: 'too few letters' }

console.log(combinedValidator('asdf1')) // {  error: true, message: 'invalid format' }

Using Predefined Higher Order Validators

You can also use predefined higher order validators found on favalid/lib/validators. These validators can be combined with your original validators.

import { tester, combine, minLength, regexp } from 'favalid';
 
 const combinedValidator = combine(
   minLength(3, () => 'too few letters'), 
   regexp(/^[a-zA-Z]+$/, () => "invalid format", {}),
   tester(() => {
     // some original validation rules
   }, () => ('original error')),
 )

Validation Result Reducers

You can aggregate validate errors with your customize error reducer using conbineWithReducer(validators, reducer, initialValue).

import { tester, combineWithReducer, minLength, maxLength, regexp } from 'favalid';

const REQUIRED_EMAIL_MESSAGE = () => "required.";

const EMAIL_REGEXP = /^(([^<>()\[\]\.,;:\s@\"]+(\.[^<>()\[\]\.,;:\s@\"]+)*)|(\".+\"))@(([^<>()[\]\.,;:\s@\"]+\.)+[^<>()[\]\.,;:\s@\"]{2,})$/i;
const REGEXP_MESSAGE = () => "invalid email.";

const EMAIL_MAX_LENGTH = 100;
const MAX_LENGTH_MESSAGE = () => "exceeds 100 letters.";

const EMAIL_MIN_LENGTH = 10;
const MIN_LENGTH_MESSAGE = () => "at least 10 letters.";

const emailValidatorWithMultipleErrorReducer = (email: string) => {
  const reducer = (prevError, currentError) => {
    if (currentError.error) {
      prevError.push(currentError);
    }
    return prevError;
  };

  return combineWithReducer(
    [
      required(REQUIRED_EMAIL_MESSAGE),
      minLength(EMAIL_MIN_LENGTH, MIN_LENGTH_MESSAGE),
      maxLength(EMAIL_MAX_LENGTH, MAX_LENGTH_MESSAGE),
      regexp(EMAIL_REGEXP, REGEXP_MESSAGE, {}),
    ],
    reducer,
    [],
  )(email);
};

console.log(emailValidatorWithMultipleErrorReducer('[email protected]')) // => []
console.log(emailValidatorWithMultipleErrorReducer('aaa')) // => [{error: true, message: 'at least 10 letters.'}, {error: true, message: 'invalid email.'}]

Examples

See src/examples.

License

This project is licensed under the Apache License 2.0 License - see the LICENSE file for details