is-nan 
ES2015-compliant shim for Number.isNaN - the global isNaN returns false positives.
This package implements the es-shim API interface. It works in an ES3-supported environment and complies with the spec.
Example
Number.isNaN = require('is-nan');
var assert = require('assert');
assert.notOk(Number.isNaN(undefined));
assert.notOk(Number.isNaN(null));
assert.notOk(Number.isNaN(false));
assert.notOk(Number.isNaN(true));
assert.notOk(Number.isNaN(0));
assert.notOk(Number.isNaN(42));
assert.notOk(Number.isNaN(Infinity));
assert.notOk(Number.isNaN(-Infinity));
assert.notOk(Number.isNaN('foo'));
assert.notOk(Number.isNaN(function () {}));
assert.notOk(Number.isNaN([]));
assert.notOk(Number.isNaN({}));
assert.ok(Number.isNaN(NaN));Tests
Simply clone the repo, npm install, and run npm test