How to get a list of month names in javascript using Intl

Question

How can I get a list of all long month names using the ECMAScript Internationalization API?

For example, if the user's locale is en-US, I'd like to get the following:

["January", "February", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December"]

Answer 1

This should do it:

function getMonthsForLocale(locale) {
    var format = new Intl.DateTimeFormat(locale, { month: 'long' })
    var months = []
    for (var month = 0; month < 12; month++) {
        var testDate = new Date(Date.UTC(2000, month, 1, 0, 0, 0));
        months.push(format.format(testDate))
    }
    return months;
}

Answer 2

My solution in 2021 with es6 Syntax

/**
 * Return list of months
 * 🌍 localeName   : name of local, f.e. en-GB, default es-MX
 *  ✅ monthFormat : short, numeric, long (Default)
 */
function monthsForLocale(localeName = 'es-MX', monthFormat = 'long') {
  const format = new Intl
     .DateTimeFormat(localeName, {month: monthFormat}).format;
  return [...Array(12).keys()]
    .map((m) => format(new Date(Date.UTC(2021, m))));
}

// testing...
console.log(monthsForLocale());
// return ['diciembre', 'enero', ..., 'noviembre' ]
console.log(monthsForLocale('en-GB', 'numeric'));
// return // ['12', '1', '2',  '3', '4',  '5', '6',  '7', '8',  '9', '10', '11']
console.log(monthsForLocale('en-GB', 'short'));
// // ['Dec', 'Jan', 'Feb','Mar', 'Apr', 'May','Jun', 'Jul', 'Aug','Sep', 'Oct', 'Nov' ]
console.log(monthsForLocale('ja-JP', 'short'));
// // ['12月', '1月',  '2月', '3月',  '4月',  '5月','6月',  '7月',  '8月','9月',  '10月', '11月']