When I downloaded your library directly from the GitHub and import it into my project everything is working fine. So it's probably some issue in the distribution package (I'm using Yarn)

Could you please post here the result of console.log(detectProxyTarget)

(This is what I see when using your library directly from GitHub instead of the npm/yarn version)

The library is exported as a CommonJS module but Node.js expects an ECMAScript Module. It is interoperable but requires some magic. Please read this Node.js docs section https://nodejs.org/api/esm.html#interoperability-with-commonjs

Had the same issue, the easiest solution for me was to switch to ts-node

Or, at least, it started "working". Returning null even for the example contract. Weird

Same issue here.

2 workarounds that are working for me:

import detectProxyTarget from "evm-proxy-detection";
const { default: detectProxy } = detectProxyTarget

...

const target = await detectProxy(
  '0xA7AeFeaD2F25972D80516628417ac46b3F2604Af',
  requestFunc
)
console.log(target) // logs "0x4bd844F72A8edD323056130A86FC624D0dbcF5b0"

import detectProxyTarget from "evm-proxy-detection";

...

const target = await detectProxy.default(
  '0xA7AeFeaD2F25972D80516628417ac46b3F2604Af',
  requestFunc
)
console.log(target) // logs "0x4bd844F72A8edD323056130A86FC624D0dbcF5b0"

Unfortunately, this doesn't work for me :-(

error TS2339: Property 'default' does not exist on type '(proxyAddress: string, jsonRpcRequest: EIP1193ProviderRequestFunc, blockTag?: BlockTag | undefined) => Promise<string | null>'.

I figured it out, in the case of typescript it's necessary to do cast:

    const target = await (<any>detectProxyTarget).default(
      address,
      requestFunc,
      "latest"
    );

Thanks for the hint @Zil-B