Sum an array of milliseconds

Question

I'm having an array of milliseconds which I want a total of. I have tried the array.reduce and use a for-loop but all I get is total gibberish when I console it or use on the site. If I get the milliseconds summed up I could convert them to seconds and, if needed, minutes.

Code:

window.timeArray = [2493, 2109, 4424, 1971, 3411, 1834, 2418]

let totalTimeSum = 0
for (let i = 0; i < window.timeArray.length; i++) {
  totalTimeSum += parseInt(window.timeArray[i])
}
document.querySelector('#score').innerText += totalTimeSum  
// 1866018660, should be 15249 - 15 sec 249 millisec

Optional code:

let totalTime = (sum, value) => sum + value
let totalTimeSum = window.timeArray.reduce(totalTime)
document.querySelector('#score').innerText += totalTimeSum  
// 1866018660, should be 15249 - 15 sec 249 millisec

why `parseInt` for numbers, `window` object and `+=` for `innerHTML`? — Nina Scholz, Dec 04 '17 at 11:08
@NinaScholz I have a Div in which I want to add the time to, hence the += to InnerText. As for the other I got the ideas from the internet... — Thomas Bengtsson, Dec 04 '17 at 11:10
also, how do you end up at 15249? the sum of those numbers *is* 18660 — Timothy Groote, Dec 04 '17 at 11:10
@TimothyGroote I added them on the calculator, might have missed one number, sorry. — Thomas Bengtsson, Dec 04 '17 at 11:12

Angel Politis · Accepted Answer · 2017-12-04T11:20:48.357

In order to accomplish what you need, you can do the following:

You can use Array.prototype.reduce to calculate the sum of the array's elements.
Then, to calculate the number of seconds, round down the quotient of the sum divided by 1000.
The remainder is the number of milliseconds remaining.

Snippet:

var
  /* Define the array. */
  timeArray = [2493, 2109, 4424, 1971, 3411, 1834, 2418],
  
  /* Calculate the sum. */
  sum = timeArray.reduce((previous, current) => previous + current, 0),
  
  /* Calculate the seconds. */
  seconds = Math.floor(sum / 1000),
  
  /* Calculate the milliseconds. */
  milliseconds = sum % 1000;

/* Set the value as text to the score element. */
document.querySelector("#score").innerText = seconds + "s " + milliseconds + "ms";

<div id = "score"></div>

Sum an array of milliseconds

1 Answers1