CODEWITHSUNDEEP
flowtype
Mark Thë Brouch
Mark Thë Brouch

Reputation: 189

How do I null check object property conditional in flow?

I have some code that looks basically like:

if ('serviceWorker' in navigator) {
  navigator.serviceWorker.register('something')
}

Which Flow throws the error Method cannot be called on possibly undefined value. Since I've done the check on serviceWorker existing, how can I have Flow recognized this is guaranteed?

Upvotes: 1

Views: 656

Answers (1)

Benjie Taluyo
Benjie Taluyo

Reputation: 61

Try this:

if ( typeof navigator.serviceWorker !== 'undefined' )

https://developer.mozilla.org/en/docs/Web/JavaScript/Reference/Operators/typeof

Upvotes: 3

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