Best way to ensure nested object value exists before calling it in Javascript

Question

For example :

data = {info: {name: john}}

How can I make sure when doing :

const name = data.info.name

That name exists, and I won't get : Can't read value name of undefined

Right now I'm doing :

let name 

if(!!data && data.info && data.info.name){
  name = data.info.name
}

But it seems messy, wondering if there's a better way

can you use lodash? – Tomasz Mularczyk Apr 09 '18 at 18:17 — Tomasz Mularczyk, Apr 09 '18 at 18:17
Lodash offers [get](https://lodash.com/docs/4.17.4#get) – Xotic750 Apr 09 '18 at 18:20 — Xotic750, Apr 09 '18 at 18:20

Ori Drori · Answer 1 · 2018-04-09T18:27:58.217

You don't need an if statement, you can assign the expression directly:

const data = {info: {name: 'john'}};
const name = data && data.info && data.info.name
console.log(name);

const data2 = {};
const name2 = data2 && data2.info && data2.info.name;
console.log(name2);

You can use destructuring assignment with defaults:

const data = {info: {name: 'john'}};

const { info: { name } = {}} = data || {};

console.log(name);

const data2 = undefined;

const { info: { name2 } = {}} = data || {};

console.log(name2);

There's also the TC39 stage 1 proposal - optional chaining, which you can use with a babel plugin:

const data = {info: {name: 'john'}};
// if any part of chain is undefined, name will be undefined
const name = data?.info?.name;

Optional chaining may one day be a nice thing. You should mention it on the marked duplicate. +1 — Xotic750, Apr 09 '18 at 18:32

Best way to ensure nested object value exists before calling it in Javascript

1 Answers1