JavaScript Date Of Birth Checker Not Working

Question

Doesn't work correctly; always outputs "above 16". I have been tweeking the if statement but couldn't figure it out. Need some help, Thanks!

function hasDateCheck() {
  let dateSpliter = document.querySelector("#dateOfBirth").value.split("-");
  console.log(`${dateSpliter[0]} ${dateSpliter[1]} ${dateSpliter[2]}`); // YYYY MM DD

  let today = new Date();
  let dd = today.getDate();
  let mm = today.getMonth();
  mm++;
  let yyyy = today.getFullYear();

  if (yyyy - dateSpliter[0] < 16 && mm - dateSpliter[1] < 0 && dd - dateSpliter[2] < 0) {
    console.log("below 16");
  } else {
    console.log("above 16");
  }
}

document.querySelector("#submit").addEventListener("click", (e) => {
  e.preventDefault();
  hasDateCheck();
});

<input name="dateOfBirth" id="dateOfBirth" type="date" required/>
<input type="submit" id="submit" value="Submit" id="formSubmit">

Why are you comparing the month and day? If the birth year is less than 16 years ago, why do the month and day matter? — Barmar, Feb 11 '21 at 07:18
You only need to check the month if the birth year is exactly 16 years ago. And you only need to check the day if it's in the current month. — Barmar, Feb 11 '21 at 07:20
use `moment.js` library and the `diff` method, it'll make things easier. — Silidrone, Feb 11 '21 at 07:20
Does this answer your question? [How can I calculate the number of years between two dates?](https://stackoverflow.com/questions/8152426/how-can-i-calculate-the-number-of-years-between-two-dates) — angel.bonev, Feb 11 '21 at 07:20
Right, it always says above 16 if the month is less than or equal to today's month, or the day is less than or equal to today's day. — Barmar, Feb 11 '21 at 07:24
As I said above, you shouldn't compare the month and day except when the year is exactly 16 years ago. — Barmar, Feb 11 '21 at 07:26

Sagar Davara · Answer 1 · 2021-02-11T07:27:39.087

1

your if condition is invalid,

replace your if condition with this,

if (yyyy - dateSpliter[0] <= 16 && mm - dateSpliter[1] <= 0 && dd - dateSpliter[2] <= 0) {
   console.log("below 16");
} else {
   console.log("above 16");
}

if you want to calculate age, then refer @Aniket answer

edited Feb 11 '21 at 07:27

answered Feb 11 '21 at 07:25

Sagar Davara

408
7
13

That's still wrong. You shouldn't compare the month and day unless the year is exactly 16 years ago. – Barmar Feb 11 '21 at 07:25

score 0 · Answer 2 · answered Feb 11 '21 at 07:24

0

Use this function to calculate age.

function age(birthday)
{
  birthday = new Date(birthday);
  return new Number((new Date().getTime() - birthday.getTime()) / 31536000000).toFixed(0);
}

answered Feb 11 '21 at 07:24

Aniket

391
5
13

score 0 · Answer 3 · answered Feb 11 '21 at 07:24

0

Just use momentjs if you can import a package

var a = moment([2007, 0, 29]);
var b = moment([2007, 0, 28]);
a.diff(b, 'years')

momentjs docs

answered Feb 11 '21 at 07:24

HexaCrop

3,863
2
23
50

Nirzar · Accepted Answer · 2021-02-11T08:29:54.257

0

if (yyyy - dateSpliter[0] > 16) {
        console.log("above 16");
    } else if (
        yyyy - dateSpliter[0] == 16 &&
        mm - dateSpliter[1] >= 0 &&
        dd - dateSpliter[2] >= 0) 
    {
        console.log("above 16");
    } else {
        guardianDetailsCheck();
        console.log("below 16");
    }
}

edited Feb 11 '21 at 08:29

answered Feb 11 '21 at 07:49

Nirzar

38
7

FZs · Answer 5 · 2021-02-11T14:38:29.273

Your condition is incorrect, because, if today's date was January 15th, 2021, and you entered January 1st, 2000, it would reject it, because the day is smaller, even though the year is greater by more than 16.

The easiest way (with the less caveats) it to convert it to a Unix timestamp (a number representing the milliseconds passed since January 1th, 1970), and compare that way:

function hasDateCheck() {
  const [YYYY, MM, DD] = document.querySelector("#dateOfBirth").value.split("-");
  const birthDate = new Date(+YYYY, +MM - 1, +DD)

  //                          year day   hour min  sec  millisec
  if(Date.now() - birthDate < 16 * 365 * 24 * 60 * 60 * 1000) {
    console.log("below 16");
  } else {
    console.log("above 16");
  }
}

document.querySelector("#submit").addEventListener("click", (e) => {
  e.preventDefault();
  hasDateCheck();
});

<input name="dateOfBirth" id="dateOfBirth" type="date" required/>
<input type="submit" id="submit" value="Submit" id="formSubmit">

You might run into issues because of leap years (for each leap year, +/- 1 day inaccuracy). You may ignore this problem (few days usually don't cause problems), implement a more complex checking behavior, or reduce the inaccuracy by adding 4 days to the date (there are approximately 16 / 4 = 4 leap years in a 16-year range):

function hasDateCheck() {
  const [YYYY, MM, DD] = document.querySelector("#dateOfBirth").value.split("-");
  const birthDate = new Date(+YYYY, +MM - 1, +DD)

  //                           year day        hour min  sec  millisec
  if(Date.now() - birthDate < (16 * 365 + 4) * 24 * 60 * 60 * 1000) {
    console.log("below 16");
  } else {
    console.log("above 16");
  }
}

document.querySelector("#submit").addEventListener("click", (e) => {
  e.preventDefault();
  hasDateCheck();
});

<input name="dateOfBirth" id="dateOfBirth" type="date" required/>
<input type="submit" id="submit" value="Submit" id="formSubmit">

JavaScript Date Of Birth Checker Not Working

5 Answers5