You say you don't necessarily know that 'key2' is in position [1]. Well, it's not. Position 1 would be occupied by myHash[1].
You're abusing JavaScript arrays, which (like functions) allow key/value hashes. Even though JavaScript allows it, it does not give you facilities to deal with it, as a language designed for associative arrays would. JavaScript's array methods work with the numbered properties only.
The first thing you should do is switch to objects rather than arrays. You don't have a good reason to use an array here rather than an object, so don't do it. If you want to use an array, just number the elements and give up on the idea of hashes. The intent of an array is to hold information which can be indexed into numerically.
You can, of course, put a hash (object) into an array if you like.
myhash[1]={"key1","brightOrangeMonkey"};