Define global function in module

Question

I can define a global function in a non-module file:

foo.ts:

function foo() {}

I can call that function from a file bar.ts without importing foo.ts:

bar.ts:

foo(); // call global function foo

However, as soon as I import another module into foo.ts, foo.ts is turned into a module and the global definition disappears. Resulting in an error in bar.ts when trying to call foo.

How can I define a global function in a module that is global across the entire project without importing it.

EDIT:

I know about the declare global syntax, but in that case I would need to write every function signature twice: Once to declare it globally and once to bind it to globalThis. I am looking for something with less boilerplate.

Would [this](https://stackoverflow.com/questions/47736473/how-to-define-global-function-in-typescript) help? — HeySora, Aug 29 '20 at 22:15
I saw that “declare global” trick, but you have to write the signature twice. — user3612643, Aug 29 '20 at 22:16

score 0 · Accepted Answer · answered Sep 03 '20 at 09:32

0

It looks like declare global is really required in such a case. The only (verbose) solution I found is:

declare global {
  function foo(): void;
}

globalThis.foo = () => {};

answered Sep 03 '20 at 09:32

user3612643

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Define global function in module

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