JavaScript - format current Date to yyyy-mm-dd hh-mm-ss-SSS

In this article, we would like to show you how to format the current Date to yyyy-mm-dd hh-mm-ss-SSS in JavaScript.

Quick solution:

// ONLINE-RUNNER:browser;

function toString(number, padLength) {
    return number.toString().padStart(padLength, '0');
}

let date = new Date();

let dateTimeNow =
                 toString( date.getFullYear(),     4 )
        + '_'  + toString( date.getMonth() + 1,    2 )
        + '_'  + toString( date.getDate(),         2 )
        + '__' + toString( date.getHours(),        2 )
        + '_'  + toString( date.getMinutes(),      2 )
        + '_'  + toString( date.getSeconds(),      2 )
        + '_'  + toString( date.getMilliseconds(), 3 )
;

// 2021_05_23__19_15_02_864
console.log(dateTimeNow);

Example output:

2021_05_23__19_15_02_864

The same code wrapped in the method for quick copy / paste:

// ONLINE-RUNNER:browser;

function getDateInFormat_yyyy_mm_dd_hh_mm_ss_SSS() {

    function toString(number, padLength) {
        return number.toString().padStart(padLength, '0');
    }

    let date = new Date();

	let dateTimeNow =
                 toString( date.getFullYear(),     4 )
        + '_'  + toString( date.getMonth() + 1,    2 )
        + '_'  + toString( date.getDate(),         2 )
        + '__' + toString( date.getHours(),        2 )
        + '_'  + toString( date.getMinutes(),      2 )
        + '_'  + toString( date.getSeconds(),      2 )
        + '_'  + toString( date.getMilliseconds(), 3 )
	;

    return dateTimeNow;
}

console.log(getDateInFormat_yyyy_mm_dd_hh_mm_ss_SSS());