In order to prevent using an object's value that doesn't exist (which would throw an error), I usually do something like this:

if(apple.details){
   // do something with apple.details
}

and it normally works fine. But if it's about a "object's object's value", like apple.details.price, that doesn't work, because if not even .details exists, the if() would throw an error.

What can I do or is there generally a better way to do this?

In order to prevent using an object's value that doesn't exist (which would throw an error), I usually do something like this:

if(apple.details){
   // do something with apple.details
}

and it normally works fine. But if it's about a "object's object's value", like apple.details.price, that doesn't work, because if not even .details exists, the if() would throw an error.

What can I do or is there generally a better way to do this?

• javascript
• object
• javascript-objects

• 5 try if(apple.details && apple.details.price) – Sphinx Commented Apr 4, 2018 at 15:55

4 Answers 4

Since 2020:

The best way to solve this is using the Optional Chaining Operator

if(apple?.details) // Undefined if apple does not exist

Suggestion of lodash is no longer required when using runtime patible with ES2020 i.e. Most browsers today & node>14.5

You can do chain:

if (apple && apple.details && apple.details.price) { ... }

But it's not convenient if the chain is long. Instead you can use lodash.get method With lodash:

if (get(apple, 'details.price')) { ... }

You may try solution of @Sphinx

I would also suggest _.get(apple, 'details.price') of lodash, but surely it is not worth to include whole library for simple project or few tasks.

_.get() function also prevents from throwing error, when even apple variable is not defined (undefined)

You would have to check each parent object prior to checking the nested child object, i.e., if (a && a.b && a.b.c) {}

If you're using LoDash, you can use the _.get function with an optional default:

let obj = {'a': {'b': {'c': 42} } };
let result = _.get(obj, 'a.b.c'); // 42
let result2 = _.get(obj, 'a.b.d'); // undefined
let result3 = _.get(obj, 'a.c.d', null); // null

If you're not using LoDash, you can implement a simplified version of _.get as shown in this answer.