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If your code isn't working as the tutorial describes, you can replace it with a working version. This will overwrite your code entirely.
knockout.js helps you simplify dynamic JavaScript UIs using the Model-View-ViewModel (MVVM) pattern.
This website is a set of interactive coding exercises to help you quickly learn how to benefit from knockout.js and MVVM.
To download knockout.js, or for full documentation, see the project's main site.