JS Functional validation library

Installation

npm install fun-validation

yarn add fun-validation

Usage

This library exports a bunch of small validation functions that all have the following signature:

(value: any) => boolean
// or when the validation requires additional parameters, we have currying:
(n:number) => (value: any) => boolean

So you would call a function like this:

import { isEmail } from 'fun-validation';

const isEmailValid = isEmail(someString);

The library also exports the validate function.

This function has the following signature:

(value: any, rules) => validationResult;

Where:

• rules must have the same shape as the value that was passed in
• and consequently the validationResult will also be in that same shape

Meaning:

• If the value is a primitive (string, number...etc), the rules must be a validation fn with the signature: (value: any) => boolean, and the validationResult will be a boolean

import { validate, isString, isInteger, isNumberMax } from 'fun-validation';

const someString = 'this is a string';

validate(someString, isString); // returns boolean

// or, you can compose your own validation fn

const someNumber = 3;

validate(someNumber, value => isInteger(value) && isNumberMax(5)(value)); // returns boolean

• If the value is an object (a plain object), the rules must an object with the same shape as value but the leaf nodes (primitives) have validation fns as values, and the validationResult will be and object in the same shape

import { validate, isString } from 'fun-validation';
import { isDate } from 'date-fns';

const user = {
  name: 'Dusan',
  dateOfBirth: new Date(1992, 9, 2),
};

const rules = {
  name: isString,
  dateOfBirth: isDate,
};

const result = validate(user, rules);

// result
{
  name: boolean;
  dateOfBirth: boolean;
}

• If the value is an array, the rules must an array with two elements. First element is a validation fn and is used to validate the array itself (for example length of the array). The second element corresponds to the shape of the element in the value array. The validationResult will be an array with the first element as boolean (result of validating the array itself), and the second element as an array of booleans (result of validation for each of the elements in the value array).

import { validate, isArray, isString, isInteger } from 'fun-validation';

// array of primitives

const hobbies = ['tennis', 'basketball'];

const rules = [isArray, isString];

const result = validate(hobbies, rules);

// result
[true, [true, true]];

// array of objects

const friends = [
  { name: 'Dusan', age: 29 },
  { name: 'Peter', age: 33 },
];

const rules = [isArray, { name: isString, age: isInteger }];

const result = validate(friends, rules);

// result
[
  true,
  [
    { name: true, age: true },
    { name: true, age: true },
  ],
];

You get the picture!

So, to recapitulate:

• The rules must be of the same shape as value with the leaf nodes (primitives) being functions that look like this: (value: any) => boolean
• The validationResult is more or less of the same shape as value and rules (except in the case of arrays) while the leaf nodes are always booleans

API

const validate: (value: any, rules) => validationResult

const isString: (value: any): boolean;

const isStringLongerThan: (len: number) => (value: any) => boolean

const isStringShorterThan:(len: number) => (value: any) => boolean

const isStringOfLength: (len: number) => (value: any) => boolean

const isStringOfMinLength: (len: number) => (value: any) => boolean

const isStringOfMaxLength:(len: number) => (value: any) => boolean                                                                                                       7

const isFunction: (obj: any) => boolean

const isObject: (value: any) => boolean

const isPromise: (value: any) => boolean

const isArray: (value: any) => boolean

const isArrayLongerThan: (len: number) => (value: any) => boolean

const isArrayShorterThan: (len: number) => (value: any) => boolean

const isArrayOfLength: (len: number) => (value: any) => boolean

const isArrayMinLength: (len: number) => (value: any) => boolean

const isArrayMaxLength: (len: number) => (value: any) => boolean

const isNumber: (value: any) => boolean

const isInteger: (value: any) => boolean

const isFloat: (value: any) => boolean

const isNumberMoreThan: (n: number) => (value: any) => boolean

const isNumberLessThan: (n: number) => (value: any) => boolean

const isNumberEqual: (n: number) => (value: any) => boolean

const isNumberMin: (n: number) => (value: any) => boolean

const isNumberMax: (n: number) => (value: any) => boolean

const isPattern: (regex: RegExp) => (value: any) => boolean

const isEmail: (value: any) => boolean

const isUrl: (value: any) => boolean