Design a function `createCounter` that takes an optional starting number.

Create a function called `useBoolean` that manages a boolean state.

Create a utility function called useCounter that helps you manage a numeric counter. It should provide methods to increase, decrease, reset, and directly set the counter value.

Write a function called mean that calculates the average value of all numbers in an array. If the array is empty, the function should return NaN.

The built-in JavaScript method `Function.prototype.call()` allows you to invoke a function with an explicit `this` value and arguments passed one by one. Your task: Implement a custom version named `Function.prototype.myCall`. ⚠️ You should not use the native `call` method internally.

Write a function `minBy(array, iteratee)` that looks through an array and returns the element for which the provided iteratee function produces the smallest value. ⚠️ If the iteratee returns `null` or `undefined` for every element, the function should return `undefined`. **Examples:** ```js minBy([2, 3, 1, 4], (num) => num); // => 1 minBy([{ n: 1 }, { n: 2 }], (o) => o.n); // => { n: 1 } minBy([{ n: 1 }, { n: 2 }], (o) => o.m); // => undefined ```