Remove random parts of an object (Chaos Monkey Style)

I have a JavaScript object e.g.:

const testFixture = {
  a: [
    {b:1},
    {b:2},
    {b:3},
  ],
  b: {c: {d: 44, e: "foo", f: [1,2,3]}}
  c: 3,
  d: false,
  f: "Blah",
}

I'd like to have a function I could pass this object to that would mutate it to remove random properties from it, so that I can test whether the thing that uses this object displays an error state, rather than silently erroring.

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Edit:

To be clear, I mean any deeply nested property. e.g. it might remove a.b.c.d.e.f[1] or a[2].b

---

Edit 2:

Here's a buggy solution I'm working on based on ideas from Eureka and mkaatman's answers.

It seems to be changing key names to "undefined" which I wasn't expecting. It's also changing numbers to {} which I wasn't expecting. Not sure why.

var testFixture2 = {
  a: [{
      b: 1, c: 2
    },
    {
      b: 2, c: 2
    },
    {
      b: 3, c: 2, d: "bar"
    },
  ],
  b: {
    c: {
      d: 44,
      e: "foo",
      f: [1, 2, 3]
    }
  },
  c: 3,
  d: false,
  f: "Blah"
};


function getRandomIndex(max) {
  return Math.floor(Math.random() * max);
}

function chaosMonkey(thing) {
  if (typeof thing === "object") {
    console.log("object", Object.keys(thing).length, thing);
    const newlyDeformedObject = { ...thing};
    // Make a list of all the keys
    const keys = Object.keys(thing);
    // Choose one at random
    const iKey = getRandomIndex(keys.length);
    let target = newlyDeformedObject[keys[iKey]];
  
    const shouldDelete = getRandomIndex(3) === 0;
    if (shouldDelete) {
      delete target;
      console.log("Object deleted", keys[iKey]);
    } else {
     console.log("+++ Going deeper", thing);
      newlyDeformedObject[keys[iKey]] = chaosMonkey({ ...newlyDeformedObject[keys[iKey]] });
    }
    return newlyDeformedObject;
  } else if (typeof thing === "array") {
    console.log(array);
    const iKey = getRandomIndex(thing.length);
    const shouldDelete = getRandomIndex(3) === 0;
    if (shouldDelete) {
      delete array[iKey];
      console.log("Array deleted", iKey);
    } else {
      array[iKey] = chaosMonkey(array[iKey]);
      return array;
    }
  } else {
    //@todo do something bad based on type e.g. number -> NaN, string -> '', but these are less likely to break something
    delete thing;
    return;
  }
}

console.log(JSON.stringify(chaosMonkey(testFixture2), null, 2));

NB: the chances of any object key or array item being recursed into are equal, in order to make modifications equally likely anywhere in the object.

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