JSFiddle - React, Tailwind, and code Playground

CSS

span {
    margin-right: 1em;
    display: inline-block;
}

.pass {
    color: green;
}

.fail {
    color: red;
}

JavaScript

var i,
    body = document.body,
    span = document.createElement('span'),
    re = /^[+-]?0*([0-9]{1,3}|1[0-9]{3}|20[0-4][0-9]|205[0-5])$/,
    extras = [
        'not a number',
        '+1984',
        20000,
        -20000
    ];

for(i = -2060; i < 2060; i++) {
    span.textContent = i;
    span.className = re.exec('' + i) ? 'pass' : 'fail';

    body.appendChild(span);
    
    span = document.createElement('span');
}

for(i = 0; i < extras.length; i++) {
    span.textContent = extras[i];
    span.className = re.exec('' + extras[i]) ? 'pass' : 'fail';
    
    body.appendChild(span);
    
    span = document.createElement('span');
}