Javascript Undefined Check Shorthand

Question

I am looking for a way to default a javascript value if something in an object with 3+ depth is undefined. For instance, something like this:

var finalData = {};
const data = {};
finalData.transactions = data.b.transactions || [];

instead of:

var finalData = {};
const data = {};
if (data.b)
    finalData.transactions = data.b.transactions || [];
else
    finalData.transactions = [];

The problem with the first line is it will fail with an undefined access issue if data does not have a child named b.

The most I can think of is using a ternary comparison – Lixus Oct 24 '17 at 14:21 — Lixus, Oct 24 '17 at 14:21

score 4 · Accepted Answer · answered Oct 24 '17 at 14:21

4

You can achieve this by combining && and ||:

finalData.transactions = (data && data.b && data.b.transactions) || [];

answered Oct 24 '17 at 14:21

Nico

this will fail if `data.b.transactions ` is a `boolean` type and the value of `transactions ` is false – Akbar khan May 17 '23 at 14:03

score 1 · Answer 2 · answered Oct 24 '17 at 14:21

1

You can do it like below:

var finalData = {};
const data = {};
finalData.transactions = data.b && data.b.transactions || [];

answered Oct 24 '17 at 14:21

Faly

2 Answers2