In this Hasty Treat, Scott and Wes talk about nothing — null, undefined, void, false, 0, ‘’, NaN, [], {}, never — all sorts of values that could mean the things that do not exist.

Prismic - Sponsor

Prismic is a Headless CMS that makes it easy to build website pages as a set of components. Break pages into sections of components using React, Vue, or whatever you like. Make corresponding Slices in Prismic. Start building pages dynamically in minutes. Get started at prismic.io/syntax.

LogRocket - Sponsor

LogRocket lets you replay what users do on your site, helping you reproduce bugs and fix issues faster. It’s an exception tracker, a session re-player and a performance monitor. Get 14 days free at logrocket.com/syntax.

Show Notes

03:35 - Undefined

Implicitly nothing
A variable declared, but not set is undefined

04:25 - Null

Explicitly nothing

04:41 - Null vs Undefined

Null has a value of nothing
Undefined does not have a value
You can set variables to either
- If you want to set a score variable to nothing, set it to null
- If you want to un-set a value, set it to undefined
- == will check if a value is either null or undefined

05:35 - Void

In Javascript
- You can pop void in front of calling a function and it will return undefined (even if that function returns a value)
- I’ve seen it on links that go nowhere (don’t do this — use a button)
- To prevent an arrow function from leaking
- onSubmit="javascript:void()" is a quick-n-easy prevent default on forms
In Typescript
- Void is when you don’t care about what is returned from a function, or if nothing is returned
- A click handler that goes off and does stuff (side effect) can return void

09:15 - Never (in Typescript)

Some functions will never return:
- Functions that throw errors
- Functions that have infinite loops
- Also, unreachable variables have a type of never
  - if(true == false) { let var = 'this will never be true'; }

11:05 - Falsy values

0, -0, 0n
false
‘’ (empty string)
Empty array
- Is a value
- Its .length can be falsy
Empty object
- Is a value
- Its object.keys(object) length can be falsy (0)

Tweet us your tasty treats!

Scott’s Instagram
LevelUpTutorials Instagram
Wes’ Instagram
Wes’ Twitter
Wes’ Facebook
Scott’s Twitter
Make sure to include @SyntaxFM in your tweets

Hasty Treat - A Podcast About Nothing

Syntax - Tasty Web Development Treats