IsNumberStrict - check if something is a number

Designed to strictly check if the value is a number. Works with Number objects, hex, and so on. Returns false for string and other not numbers like {}, undefined, NaN

Install

1npm i is-number-strict

Usage

JavaScript with require syntax

1const isNumber = require('is-number-strict').default;
2
3console.assert(isNumber(5));
4console.assert(!isNumber('5'));

JavaScript with import syntax

1import isNumber from "is-number-strict";
2
3console.assert(isNumber(5));
4console.assert(!isNumber('5'));

What problem it solves

This tiny lib tries to make type assertion little bit more predictable and remove NaN from your calculations.

1typeof new Number(42);
2> 'object'

But it is working as good old number

1new Number(5) * new Number(6);
2> 30

So:

1isNumberStrict(new Number(5));
2> true

But:

1isNumberStrict('5');
2> false

And

1isNumberStrict(NaN);
2> false

Why didn't you treat '5' as a number? '5' + 5 = 10! Yes, but 5 + '5' = '55' and 5 * '5' = NaN. I don't want to see NaN or '55' in my calculations.

So if you want to have more predictable type checking - check my tests and welcome!

Some wired cases

Why do you treat new Number([]) as a number?

Because JS will evaluate it to 0, and 0 is number.

Why do you treat new number({}) as not a number?

Because JS will evaluate it to NaN and NaN is not a number according to my purposes.