Hasty Treat - A Podcast About Nothing


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.

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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)
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