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Discussion on: How to solve "window is not defined" errors in React and Next.js

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rowin1125 profile image
Rowin Mol • • Edited

Niceee!

If you don't want to have a lot of boilerplate code, you could simple write:

const isBrowser = window && window.addEventListener(.......blabla)
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and use this variable as a conditional.

Also if you use the first option, please remember to unsubscribe your eventListener in the useEffect or you gonna have a bad time 😭 .

useEffect(function onFirstMount() {
    function onScroll() {
      console.log("scroll!");
    }

    window.addEventListener("scroll", onScroll);

   return () => {
      window.removeEventListener("scroll");
    }
  }, []);
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clxrityy profile image
clxrity •

I found this only works (2024) when adding window to the dependency array.

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vvo profile image
Vincent Voyer • • Edited

Hey there Rowin, you might have a different setup but const isBrowser = window won't work at least in Next.js pre-rendering. You'll get the same error (just tried it again). I think anytime such code would go through Node.js it would fail, as shown in a REPL:

> node
Welcome to Node.js v12.18.0.
Type ".help" for more information.
> window && "ok"
Uncaught ReferenceError: window is not defined
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As for unsubscribing the listener, this is already done in the code samples from the article so maybe you missed that or there's some other place I forgot to do it?

Thanks

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teamroggers profile image
Rogier Nitschelm •

Perhaps like this?

const isBrowser = () => typeof window !== "undefined"

// node
isBrowser() // false

// browser
isBrowser() // true
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vvo profile image
Vincent Voyer •

Yes that would work indeed! Thanks :)

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vvo profile image
Vincent Voyer •

Just added a new solution and thank you note :)

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ariyou2000 profile image
ARiyou Jahan •

In a tread related to this problem in Next.JS official GitHub issue page mentioned that it is wrong to do so and you need to explicitly check typeof window !== "undefined" wherever you need it:
NextJS GitHub issues page

Consider reading my solution as well. it's inspirred by this post. So thank you Vincent for idea.
NextJS - Access window and localStorage