How display the millisecondes since my birth in JS?

Question

Today I'm training with the date in Javascript.

I displayed today's date and the milliseconds since 01/01/1970.

Now I would like to display the milliseconds since my birth, but don't know why one of my functions produces wrong results.

First one works correctly, but in the second function the milliseconds count stays fixed.

This example works:

function elapsedTime(id) {
  date = new Date()
  epoque = date.getTime()

  if (epoque < 10) {
    epoque = "0" + epoque
  }

  resultat = epoque + ' millisecondes ce sont écoulées depuis le 1er janvier 1970'
  document.getElementById(id).innerHTML = resultat
  setTimeout('elapsedTime("' + id + '");','1000')

  return true;
}

This example doesn't work:

function myBirthday(id) {
  birthday = new Date('september 15, 1986 14:29:00')
  milliseconde = birthday.getTime()

  if (milliseconde < 10) {
    milliseconde = "0" + milliseconde
  }

  resultat = milliseconde + ' millisecondes ce sont écoulées depuis ma naissance'
  document.getElementById(id).innerHTML = resultat
  setTimeout('myBirthday("' + id + '");','1000')

  return true;
}

I don't understand where is my mistake.

Thanks for help.

setTimeout uses an integer and you are passing in a string for milliseconds. — epascarello, Aug 28 '19 at 19:36
You code is just showing the same date over and over again. There is no calculation. — epascarello, Aug 28 '19 at 19:37
"september 15, 1986 14:29:00" is not a format supported by ECMAScript, see [*Why does Date.parse give incorrect results?*](https://stackoverflow.com/questions/2587345/why-does-date-parse-give-incorrect-results) You should be doing `Date.now() - new Date(1986, 8, 15, 14, 29)`. — RobG, Aug 28 '19 at 21:39

score 0 · Answer 1 · answered Aug 28 '19 at 19:37

0

To get the milliseconds since your birth, you have to subtract your birth time from the current time. You're just showing the milliseconds from the epoch to your birth time every time you call the function.

function myBirthday(id) {
  birthday = new Date('september 15, 1986 14:29:00')
  milliseconde = new Date().getTime() - birthday.getTime()
  if(milliseconde<10){
    milliseconde = "0"+milliseconde
  }
  resultat = milliseconde+ ' millisecondes ce sont écoulées depuis ma naissance'
  document.getElementById(id).innerHTML = resultat
  setTimeout('myBirthday("'+id+'");','1000')
  return true;

}

myBirthday("output");

<div id="output"></div>

answered Aug 28 '19 at 19:37

Barmar

741,623
53
500
612

Thanks ! it works! :) – Carolinedanslesnuages Aug 28 '19 at 19:45
`if(milliseconde<10){...` who will run this when they are less than 10 ms old? ;-) – RobG Aug 29 '19 at 11:13
@RobG I was wondering the same thing, but decided not to make an issue of it, so I just kept it. The original code also has that for the current time, which would require a time machine. – Barmar Aug 29 '19 at 14:00

score 0 · Answer 2 · answered Aug 28 '19 at 19:37

0

You need to deduct your birthday milliseconds from the current date milliseconds:

var birthday = new Date('September 15, 1986 14:29:00');
var now = new Date();
var difference = now - birthday;

answered Aug 28 '19 at 19:37

Kim T

5,770
1
52
79

How display the millisecondes since my birth in JS?

2 Answers2