jeena/en.javascript.info
1
0
Fork 0
Code Issues Pull requests Projects Packages Wiki Activity Actions

minor fixes

Browse source
This commit is contained in:
Ilya Kantor 2020-10-06 13:04:27 +03:00
parent 545f514790
commit f4cf5808c8
1 changed files with 5 additions and 3 deletions
Download patch file Download diff file Expand all files Collapse all files

8
1-js/04-object-basics/07-optional-chaining/article.md
View file

@ -9,17 +9,19 @@ The optional chaining `?.` is a safe way to access nested object properties, eve
If you've just started to read the tutorial and learn JavaScript, maybe the problem hasn't touched you yet, but it's quite common.
As an example, let's consider objects for user data. Most of our users enter addresses, but some did not provide them.
As an example, let's consider objects for user data. Most of our users have addresses in `user.address` property, with the street `user.address.street`, but some did not provide them.
In such case, when we attempt to get `user.address.street`, we'll get an error:
```js run
let user = {}; // the user happens to be without address
let user = {}; // the user without "address" property
alert(user.address.street); // Error!
```
Another example. In the web development, we may need to get an information about an element on the page, that sometimes doesn't exist:
That's the expected result, JavaScript works like this, but many practical cases we'd prefer to get `undefined` instead of an error (meaning "no street").
...And another example. In the web development, we may need to get an information about an element on the page, that sometimes doesn't exist:
```js run
// Error if the result of querySelector(...) is null