This is an attempt to make a shareable library to validate fundamental types with as little code as possible.

the module is a function that returns a function that returns a test, by name. The nature of the tests is that if the candidate passes the test false is returned; if not, a string is returned describing the error.

This means, "false is good, string is fail".

import validators from '@wonderlandlabs/validators';
const val = validators();
const isString = val('string');

console.log(isString('foo')); 
// false

console.log(isString(1));
// 'must be string';

Current tests include:

• string
• number
• integer
• array
• object
• map (Map class)
• set (Set class)
• boolean (true or false)
• date (Date class)
• function
• null
• undefined
• true (truthy)
• false (falsy)

is

If you want true to be returned when an item is valid, call "is". Is returns true for good data, false for bad; therefore, never returns string.

import validators from '@wonderlandlabs/validators';
const val = validators();
const isString = val.is('string');

console.log(isString('foo')); 
// true

console.log(isString(1));
// false

Expanding validators

validators uses a closured set of tests; you can expand the tests by passing a function into validators:

import validators from '@wonderlandlabs/validators';
const val = validators();
const digits = [0,1,2,3,4,5,6,7,8,9];
function isDigit(value) {
  return digits.includes(value) ? false : 'must be 0-9'
}

val('digit', isDigit);

console.log(val('digit')(2)); 
// false
console.log(val('digit')(20)); 
// 'must be 0-9'

Your custom tests are only available from the instance function you use to define the test. This is intentional, to prevent singleton issues.