JSFiddle - React, Tailwind, and code Playground

JavaScript

var tests = [
    '0',
    '1',
    '-1',
    '-1.1',
    '1.1',
    '12abc123',
    '+42',
    '0xFF',
    '5e3'
    ];


function nat(n){ return n>=0 && Math.floor(n) === +n;}

var res = tests.map(function(n){ return (n+" is ")+(nat(n)?"natural":"not natural")}).join(",<br />")

document.body.innerHTML = res;