[BUG] "typeof window" can not be the define key.

[Amour1688]

• esbuild

• webpack

[upupming]

@Amour1688 I think currently we can only use --define:window=undefined directly instead of --define:"typeof window"=undefined:

Input:

if (typeof window === 'undefined') {
  console.log('sss')
} else {
  console.log('ttt')
}
console.log(window)

esbuild test.js --define:window=undefined Output:

if (true) {
  console.log("sss");
} else {
  console.log("ttt");
}
console.log(void 0);

esbuild test.js --define:window=\"object\" Output:

if (false) {
  console.log("sss");
} else {
  console.log("ttt");
}
console.log("object");

However this will change the value of window in the compiled output, actually we only want to define typeof window, so that we can run something only on browser-side or node-side, just like process.browser and typeof window !== 'undefined' in Next.js: vercel/next.js#2473 (comment), https://github.com/vercel/next.js/blob/0fb1183973f6b818ce2972a64570ee566cbd7357/packages/next/build/babel/loader/get-config.ts#L105

[evanw]

This is not a bug. The define feature is only for replacing certain kinds of expressions. It's not a general-purpose code replacement mechanism. Changing just typeof window without changing window sounds potentially unsafe since it means code will have an inconsistent view of what the window variable is. You are welcome to define process.browser or some other thing instead.

[evanw]

Closing this issue because this is not a bug, and I don't think this feature request should be implemented because it leads to logical inconsistencies in the code that could introduce bugs and/or be confusing.