What's a chained double bang operator (`!!`) in Typescript?

Asked Oct 25 '22 at 01:58

Active Oct 25 '22 at 03:36

Viewed 763 times

I've recently ran into this TSX syntax:

<SomeElement
  onClick={() => {
    setSearchInput('')
    ref.current!!.focus()
  }}
/>

SomeElement has a type of React.ForwardRefExoticComponent<SomeInterface & React.RefAttributes<HTMLInputElement>>

ref.current has a type of React.MutableRefObject<HTMLInputElement>.current: HTMLInputElement | null

Could anyone explain what's up with the double bang (!!) before .focus()? According to linter, it is valid syntax.

Where is this documented? I've searched MDN for the list of operators and I haven't found anything relevant.
I know what a double negation is (e.g: replacement for Boolean()), but this doesn't seem to be the case. Or... is it?

edited Oct 25 '22 at 03:36

asked Oct 25 '22 at 01:58

tao

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It's a typo of `ref.current!.focus()` – CertainPerformance Oct 25 '22 at 01:59
@Certain, so you're saying it's a valid typo? And that only once would suffice? – tao Oct 25 '22 at 02:01
It's a syntactically valid typo that there probably should be a linter rule for somewhere in an ideal world, but it's such an odd occurrence that I'm not surprised if there isn't – CertainPerformance Oct 25 '22 at 02:01
1

`null!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!` is valid typescript. So is `!!!!!!!!!!!!!!!!!!!!!!!!!!!!false`. – kelsny Oct 25 '22 at 02:02
Got it. Thanks. It is, indeed, TS, I just though it's unrelated to typescript. – tao Oct 25 '22 at 02:02

What's a chained double bang operator (`!!`) in Typescript?

0 Answers0