Why do I get an undefined error when calling a function without parameter?

Question

I don't find the mistake, what am I doing wrong? It has to be a stupid and very easy reason...

When calling this function without a parameter the current year should be used in the following code but I get an 'undefined' error

function get_ostersonntag(year){
    if ((year == "") || (year == null)){
        year= new Date();
        year = year.getFullYear;

    }

    console.log(year)
  }

because `year` is passed with the value `undefined` and hence it doesn't go inside the `if` condition? — Boney, May 02 '19 at 08:34
but even when I edit the function with year default null the same error occures? function blaala(year=null){etc. — aejsi5, May 02 '19 at 08:36
What's the error? It works for me (the value of `year` becomes `undefined`, but `undefined == null` is `true`, so the `if` statement gets passed). It logs a function value for me, because `year.getFullYear` is a function - you probably meant `year = year.getFullYear()` — Robin Zigmond, May 02 '19 at 08:43
Thank you @LGSon! This was the problem. As mentioned...stupid and very easy reason :) — aejsi5, May 02 '19 at 08:45
sorry @LGSon, I'd missed your comment somehow, and just posted mine (with the same content) as an answer :/ — Robin Zigmond, May 02 '19 at 08:46

score 1 · Answer 1 · answered May 02 '19 at 08:45

Your function works fine - when you call it with no arguments, the year argument is implicitly assigned to the undefined value. And undefined == null is true, so the if block is executed.

What I suspect is confusing you is that you have returned year.getFullYear, which is a function value. I think you want to actually call this function to get the result:

function get_ostersonntag(year){
    if ((year == "") || (year == null)){
        year= new Date();
        year = year.getFullYear();

    }

    console.log(year)
  }

get_ostersonntag()

Nina Scholz · Answer 2 · 2019-05-02T08:43:23.657

0

You could check if year is falsy, that are values like empty string '', null, undefined, false, but zero 0 as well and NaN and check if year is not zero.

function get_ostersonntag(year) {
    if (!year && year !== 0) {
        return new Date().getFullYear();
    }
    return year;
}

console.log(get_ostersonntag());
console.log(get_ostersonntag(0));

edited May 02 '19 at 08:43

answered May 02 '19 at 08:34

Nina Scholz

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score 0 · Answer 3 · answered May 02 '19 at 08:46

0

Thanx all. The reason was the missing brackets after .getFullYear

answered May 02 '19 at 08:46

aejsi5

147
6

score 0 · Accepted Answer · edited May 02 '19 at 08:54

0

The only thing you missed are the parentheses after year = year.getFullYear

function get_ostersonntag(year){
    if ((year == "") || (year == null)){
        year= new Date();
        year = year.getFullYear();
    }
    console.log(year)
}

edited May 02 '19 at 08:54

kalehmann

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answered May 02 '19 at 08:46

NoParanoia

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score -1 · Answer 5 · answered May 02 '19 at 08:35

-1

you can try

function get_ostersonntag(year){
    if (!year){
        year= new Date();
        year = year.getFullYear;

    }

    console.log(year)
  }

answered May 02 '19 at 08:35

Harish

1,693
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score -1 · Answer 6 · edited May 02 '19 at 08:38

-1

Update your if condition:

function get_ostersonntag(year){
    if (!year) {
        year= new Date();
        year = year.getFullYear();
    }

    console.log(year)
  }

whenever year has falsy value (undefined, null or ''), it will go inside the if loop.

edited May 02 '19 at 08:38

SNag

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answered May 02 '19 at 08:37

Krantisinh

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Why do I get an undefined error when calling a function without parameter?

6 Answers6