JSFiddle - React, Tailwind, and code Playground

HTML

Numeric arguments / String arguments

CSS

body { 
    font: 10px "Andale Mono", "Droid Sans Mono", monospace; 
}

JavaScript

var day, month = 0, year = 2012,
    div, dateFromNumbers, dateFromString, datesAreEqual;

while (++month <= 12) {
    
    day = 0;
    
    div = document.createElement('div');
    
    div.appendChild(document.createElement('br'));
    
    div.appendChild(document.createTextNode('Month ' + month));
    
    document.body.appendChild(div);
    
    while (++day) {

        dateFromNumbers = new Date(year, month - 1, day);
        dateFromString = new Date(year + '-' + month + '-' + day);
        
        if (dateFromNumbers.getMonth() != month - 1) break;
        
        datesAreEqual = +dateFromNumbers == +dateFromString;

        div = document.createElement('div');

        div.style.color = datesAreEqual ? 'green' : 'red';

        div.appendChild(document.createTextNode(
            dateFromNumbers + ' / ' + dateFromString))

        document.body.appendChild(div);

    }
}