Round a Date() to the nearest 5 minutes in javascript

That's pretty simple if you already have a Date object:

var coeff = 1000 * 60 * 5;
var date = new Date();  //or use any other date
var rounded = new Date(Math.round(date.getTime() / coeff) * coeff)

With ES6 and partial functions it can be elegant. Choose if need to round to closest or always down/up:

const roundTo = roundTo => x => Math.round(x / roundTo) * roundTo;    
const roundDownTo = roundTo => x => Math.floor(x / roundTo) * roundTo;
const roundUpTo = roundTo => x => Math.ceil(x / roundTo) * roundTo;

const roundTo5Minutes = roundTo(1000 * 60 * 5);
const roundDownTo5Minutes = roundDownTo(1000 * 60 * 5);
const roundUpTo5Minutes = roundUpTo(1000 * 60 * 5);

const now = new Date();
const msRound = roundTo5Minutes(now)
const msDown = roundDownTo5Minutes(now)
const msUp = roundUpTo5Minutes(now)

console.log(now);
console.log(new Date(msRound));
console.log(new Date(msDown));
console.log(new Date(msUp));

Round to nearest x minutes

Here is a method that will round a date object to the nearest x minutes, or if you don't give it any date it will round the current time.

let getRoundedDate = (minutes, d=new Date()) => {

  let ms = 1000 * 60 * minutes; // convert minutes to ms
  let roundedDate = new Date(Math.round(d.getTime() / ms) * ms);

  return roundedDate
}


// USAGE //

// Round existing date to 5 minutes
getRoundedDate(5, new Date()); // 2018-01-26T00:45:00.000Z

// Get current time rounded to 30 minutes
getRoundedDate(30); // 2018-01-26T00:30:00.000Z