How do I get a copy of items in knockout observable array. Changing the copied items should not affect the original item.
What I want to do is before opening a popup, create a copy of item when the user clicks cancel button reload the original values
You can just use standard JavaScript techniques to clone your array. See the following:
Copying array by value in JavaScript
So, you can copy as follows:
var newArray = viewModel.observableArray().slice(0);