Javascript Undefined Check Shorthand [duplicate]

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.

Answer 1

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

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

Answer 2

You can do it like below:

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