What is the best way of cloning/copying an observablearray in knockoutJS?

To clone an observableArray you would want to do:

var viewModel = {
    array1: ko.observableArray(["one", "two"]),
    array2: ko.observableArray()
};

viewModel.clone = function() {
   viewModel.array1(viewModel.array2.slice(0));
};

If you want to just do a copy, then you would do:

viewModel.array1(viewModel.array2());

The problem with the second example is that the underlying array is the same, so pushing to array1 or array2 would result in both having the new value (as they both point to the same array).