How to check object has some property/object in typescript?

Question

I have to check

if (!window.MSStream) ...

but I get error in TypeScript, intellisense underlines MSStream object, because it is not declared - and that's exactly my point to check - but I can't build app in Angular2 because of that error. How can I "cheat" typescript or force him not to be so strict and act like regular javascript and just do that check and leave me alone...

Gregor Woiwode · Accepted Answer · 2017-06-29 14:25:59Z

3

MSStream is not part of the type definitions provided for window. You can either add this type on your own or you access this property via square brackets. Then the typescript compiler should be fine.

if (!window['MSStream']) { /* do something */ }

answered Jun 29, 2017 at 14:25

Gregor Woiwode

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2 Comments

Dalibor Over a year ago

You're right, it worked! Although I was SURE I tried that before... obviously I didn't :)

Gregor Woiwode Over a year ago

I know what you mean. :-) Sometimes I run into the same issues. ;-) Happy Coding!

ruben.moor · Accepted Answer · 2024-03-15 20:32:09Z

1

if (!window['MSStream']) { /* do something */ }

doesn't work anymore. I get

Element implicitly has an 'any' type because index expression is not of type 'number'.

But this works:

(window as Window & {MSStream?: { /* props go here */}}).propXYZ

answered Mar 15, 2024 at 20:32

ruben.moor

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2 Comments

Dalibor Over a year ago

Wow! This really looks opposite of elegant. Well, thanks for the info

ruben.moor Over a year ago

@Dalibor well the beauty is in the eye of the beholder :) Type-safety comes at a cost here. But it DOES make your intentions more explicit.

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