Bounty: Help grug brained dev with JS - Amount negotiable.

sample.js

function foo() {
  let fetchCopy = window.fetch;
  return function() {
    return fetchCopy('http://example.com');
  };
}

let boo = foo();

function bar() {
  // Somehow intercept fetch call from fetchCopy.
  // Conditions:
  // - You cannot change foo
  // - You cannot override foo (It's a function hidden deep within obfuscated JS)
  // - It works in an electron app
  // - You can only write in this bar function. Nothing else can change
  // Why?
  // This is for github.com/acheong08/rev-obsidian-sync-plugin. You can check it out if interested.
  // A recent update from ObsidianMD broke the current implementation and I can't figure it out.
  // I'm not a JavaScript dev.
}

bar();

boo();

gotcha. Might be overkill, but try this. It works with the toy example, but see if it will work in your real-world use case. There's a chance that it needs to be modified to use the same context (this object) of foo.

function bar() {
    const fooCode = foo.toString()

    const myFetch = (...args) => {
        console.log('intercepted', args)
        return window.fetch(...args)
    }

    const fooCodeModified = fooCode.replace('let fetchCopy = window.fetch;', 'let fetchCopy = myFetch;');

    const evalCode = `boo = (${fooCodeModified})(/* args here */)`

    eval(evalCode)
}

Good effort but I think the specifics of this case (extreme obfuscation & no reliable access to foo itself) makes this pretty much impossible. I've thought up another solution without having to intercept the initial login request