let date = new Date(2020, 05, 21); // 2020-06-21
let longMonth = date.toLocaleString('en-us', { month: 'long' }); /* June */
let shortMonth = date.toLocaleString('en-us', { month: 'short' }); /* Jun */
let narrowMonth = date.toLocaleString('en-us', { month: 'narrow' }); /* J */

var  months = ["January", "February", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December"];
var d = new Date();
var monthName=months[d.getMonth()]; // "July" (or current month)

date('m');

var Xmas95 = new Date();
var options = { month: 'long'};
console.log(new Intl.DateTimeFormat('en-US', options).format(Xmas95));
// December
console.log(new Intl.DateTimeFormat('de-DE', options).format(Xmas95));
// Dezember