what-is

NOTE: The package what-is was renamed to wots. Please, consider installing the renamed version.

why?

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

how?

npm install --save what-is

and then

var whatis = require('what-is');

// ...

if (whatis(myNotAlwaysNumericVariable) === 'NaN') {
    // do some stuff
}

what?

whatis() 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)	throws error (to be fixed)
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