JavaScript Array destructuring assignment and null value

Question

I'm using an external service getListOfItemsFromServiceA which accepts an id (of user) and returns a list of 5 items (exactly 5) associated to this user.

I used Array destructuring assignment to set the value of those items which is working fine like this (just an example):

var item1, item2, item3, item4, item5;
//var result = getListOfItemsFromServiceA(1622);
var exampleResult = ['item1', 'item2', 'item3', 'item4', 'item5'];
[item1, item2, item3, item4, item5] = exampleResult;
console.log(item1, item2, item3, item4, item5);

The problem I have is that in some cases getListOfItemsFromServiceA(id) returns null for example when the id is not found in the database. So my code is not working:

var item1, item2, item3, item4, item5;
//var result = getListOfItemsFromServiceA(1622);
var exampleResult = null;
[item1, item2, item3, item4, item5] = exampleResult;
console.log(item1, item2, item3, item4, item5);

Is there a way to solve this using Array destructing syntax instead of adding an if condition like if(getListOfItemsFromServiceA(1622) !== null)?

Note

I can't change the code of getListOfItemsFromServiceA.

why you don't want to add if condition?

error404
– error404

2017-07-14 14:50:02 +00:00
Commented Jul 14, 2017 at 14:50 — error404
– error404, Commented Jul 14, 2017 at 14:50

Henrique Oecksler Bertoldi · Accepted Answer · 2017-07-14 14:49:15Z

8

Do this:

[item1, item2, item3, item4, item5] = exampleResult || [];

answered Jul 14, 2017 at 14:49

Henrique Oecksler Bertoldi

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4 Comments

Jeremy Thille Over a year ago

Not very elegant in the sense that it produces undefined, undefined, undefined, undefined, undefined

Henrique Oecksler Bertoldi Over a year ago

I know, indeed. But perhaps this exactly what he wants.

Jeremy Thille Over a year ago

True, OP asks "Is there a way to solve it?" and this solves it :)

Ala Eddine JEBALI Over a year ago

@HenriqueOeckslerBertoldi thanks this is what I need. It works!

Jeremy Thille · Accepted Answer · 2017-07-14 14:55:11Z

3

You can add a fallback if exampleResult is null :

var item1, item2, item3, item4, item5;
var exampleResult = null;
[item1, item2, item3, item4, item5] = exampleResult || [];
console.log(item1, item2, item3, item4, item5);

This produces undefined, undefined, undefined, undefined, undefined.

You can also set default values to the destructured variables :

var item1, item2, item3, item4, item5;
var exampleResult = null;
[item1="", item2="", item3="", item4="", item5=""] = exampleResult || [];
    console.log(item1, item2, item3, item4, item5);

answered Jul 14, 2017 at 14:55

Jeremy Thille

26.4k12 gold badges48 silver badges64 bronze badges

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