CODEWITHSUNDEEP
javascriptnull
Tymokhovcev Valeriy
Tymokhovcev Valeriy

Reputation: 3

Is it necessary to use null two times at the end of the code?

I have one question. Help me, please.

I have code in my teaching proggram:

alert(user.address ? user.address.street ? user.address.street.name : null : null);

But I can't understand, why he used "null" two times at the end of the code?

I understand that if user.adress - exist, then check whether user.address.street exist, if user.address.street - exist, then check whether user.address.street.name exist, if not alert - null.

But why did he write second null?

Upvotes: 0

Views: 122

Answers (2)

user22074198
user22074198

Reputation: 1

here user.address ? is condition sentence that have two operand. the first one is whole

user.address.street ? user.address.street.name : null

If the condition is true we'll go deeply to this sentence that is a condition sentence by own and have two operand again: first one is user.address.street.name (if nested condition is true) and the second one is null (if the nested condition is false). the last null is the second operand of user.address ? if it's false.

Upvotes: 0

Schokokuchen Bäcker
Schokokuchen Bäcker

Reputation: 906

The ? operator is a shorthand for an if-else assignment.

alert(user.address ? user.address.street ? user.address.street.name : null : null);

Is the short form for:

let res;
if (user.address) {
    if (user.address.street) {
          res = user.address.street.name;
    } else {
          res = null;
    }
} else {
    res = null;
}
alert(res);

In javascript there is also the 'optional chaining operator' which is probably what you want:

alert(user?.address?.name);

Which only access the objects properties if they are not null, otherwise returns null.

Upvotes: 3

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