why?

The library was written as a simple coding exercise, but then appeared useful to share 😉

how?

npm install --save wots

and then

// use as ES6 module
import wots from 'wots';

// use in NodeJs
var wots = require('wots');

// use as global variable via UnPKG
<script src="https://unpkg.com/wots"></script>

// ... then ...

if (wots(myNotAlwaysNumericVariable) === 'NaN') {
  // do some stuff
  // e.g. console.log('I cannot count on it')
} else if (wots(myNotAlwaysNumericVariable) === 'Infinity') {
  // do some other stuff
  // e.g. console.log('Please do not force me to use this value in a loop!')
}

what?

wots() function returns reasonable type names for tested values:

description	input	result
null	null	'null'
undefined	undefined	'undefined'
strings	'foo'	'string'
	''	'string'
	['Hello', 'world!'].join(' ')	'string'
	new String()	'string'
numbers	5	'number'
	parseInt(42)	'number'
	new Number('3')	'number'
	NaN	'NaN'
	Infinity	'Infinity'
	1 / -0	'Infinity'
boolean values	false	'boolean'
	!!nonEmptyVariable	'boolean'
	new Boolean('0')	'boolean'
regular expressions	/^test$/g	'regexp'
	new RegExp('needle', 'i')	'regexp'
arrays	['foo', 'bar', 'baz']	'array'
	new Array(10)	'array'
objects	{ foo: 'bar'}	'object'
	{}	'object'
	new Object()	'object'
	Object.create(null)	'object
functions	function () {}	'function'
	new Function('return null')	'function'
date objects	new Date()	'date'
errors	new Error('error!')	'error'
	new TypeError('type error!')	'error'
arguments objects	(function(){return arguments;})()	'arguments'
class constructors	new MyClass()	'myclass'
	new Buffer()	'buffer'
	new XMLHttpRequest()	'xmlhttprequest'
promises	new Promise(function() {})	'promise'
	Promise.resolve('data')	'promise'
	Promise.reject(new Error('Oop!'))	'promise'

Note: for more examples see test file

Since version 0.2.0 the library also exposes static methods listed below:

wots.isNull()
wots.isUndefined()
wots.isString()
wots.isNumber()
wots.isNaN()
wots.isInfinity()
wots.isBoolean()
wots.isRegExp()
wots.isArray()
wots.isObject()
wots.isFunction()
wots.isDate()
wots.isError()
wots.isArguments()
wots.isPromise()

the name

wots basically stands for what is but is shorter 😉