If Array.find doesn’t find the matching element, it returns undefined. The problem is when you try and pass the result of a find call into a function with a default parameter. If find results in undefined, the default value of the parameter will overwrite it. This isn’t the case if you pass in null. So then you have to end up doing a short-circuit ||, i.e. […].find(x => notFound) || null. Not great. I can’t think of any other javascript functions that return undefined. I also can’t think of a reason that it should return undefined over null.