typeof window == "undefined" throws an error while using ts-node

Question

I have some code within which I'm using typeof window == "undefined" to check whether there is a browser environement. When I'm launching this code with ts-node, I'm getting this:

typings/Console.ts:36:10 - error TS2304: Cannot find name 'window'.

36      typeof window == "undefined"
               ~~~~~~

AFAIK typeof is kind of operator that is safe to use with not defined variables, and it works well both in browser and in NodeJS environement. But as far as I start to use it with ts-node, it starts to throw.

My tsconfig.json

{
    "compilerOptions": {
        "module": "CommonJS",
        "target": "es5",
        "moduleResolution": "node",
        "baseUrl": "src",
        "allowSyntheticDefaultImports": true,
        "noImplicitAny": true,
        "strict": false,
        "sourceMap": true,
        "traceResolution": true,
        "experimentalDecorators": true,
        "emitDecoratorMetadata": true,
        "strictNullChecks": true,

        "allowJs": false,
        "declaration": false,
        "removeComments": true,
        "noLib": false,
        "preserveConstEnums": true,
        "suppressImplicitAnyIndexErrors": true,
        "types": [ "node" ],
        "lib": [ "es6" ],
        "downlevelIteration": true,
        "resolveJsonModule": true,
        "typeRoots": [
            "../node_modules/@types"
        ]
    }
}

So, what the trick? Thanks in advance!

@LukaKostic This won't help because window is still not defined. — Limbo
– Limbo, Commented May 18, 2020 at 13:59
@kalit well, don't understand why, but it helped. Seems more like a bug than like an expected behavior. Thank you! Post your comment as answer to allow me to mark it as right answer :) — Limbo
– Limbo, Commented May 18, 2020 at 14:02
@Limbo but there is only check type is defined, not object, maybe somewhere later is defined — kalit
– kalit, Commented May 18, 2020 at 14:03

kalit · Accepted Answer · 2020-05-18 14:03:55Z

5

try add to lib in tsconfig "DOM"

answered May 18, 2020 at 14:03

kalit

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1 Comment

Ivan Kleshnin Jun 3 at 12:51

It allows developers to use other DOM-specific, unrelated types by mistake.

Caramel · Accepted Answer · 2020-05-18 14:05:08Z

4

For me it worked to first declare the variable to TypeScript, so:

declare var window;

if(typeof window == "undefined"){
// code
}

answered May 18, 2020 at 14:05

Caramel

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2 Comments

Limbo Over a year ago

Hello and thank you for your answer. Unfortunately, this approach is not good when your project is basically browser oriented and you have several similar conditions across the sources (e.g. typeof document != "undefined", typeof navigator != "undefined, etc.). As answered by @kalit the problem could be solved by adding "DOM" to "lib" property of tsconfig.json.

Limbo Over a year ago

Generally speaking, the typeof operator in Typescript is useless because it does not allow you to be used with totally not defined variables, that goes in contrast with vanilla JS typeof operator.

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