AI solution for JavaScript Coding Question on BFE.dev
90. write your own `instanceof`

Here is one possible solution for implementing myInstanceOf:

function myInstanceOf(obj, cls) {  while (obj !== null) {    if (obj.constructor === cls) return true;    obj = Object.getPrototypeOf(obj);  }  return false;}

This function takes an object obj and a class constructor cls, and returns true if obj is an instance of cls (or a subclass of cls), and false otherwise.

The function works by walking up the prototype chain of obj, checking each constructor along the way against cls. If obj.constructor === cls, then obj is an instance of cls, so we return true. If we reach the end of the prototype chain (i.e. obj === null) without finding a matching constructor, then obj is not an instance of cls, so we return false.

Note that this implementation does not handle the case where cls is not a constructor (e.g. if it is not a function). In that case, the function might throw an error, or it might return false. To handle this case, we could add some additional checks at the beginning of the function to make sure that cls is a function, or we could return false early if it is not.

Overall, this implementation should work for most cases where instanceof would be used. However, it is worth noting that instanceof and myInstanceOf are not guaranteed to behave exactly the same way in all cases, especially when dealing with objects that have unusual prototype chains. So, it is always a good idea to test your code carefully and make sure that it is working as expected.