Knockout is a JavaScript library that helps create rich and responsive user interfaces with a clean underlying data model. The library also helps to implement dynamic update of UI sections (e.g., changing depending on the user’s actions or when an external data source changes) in more simple and maintainable manner.

Knockout provides the following headline features: elegant dependency tracking - automatically updates the right parts of the UI whenever the data model changes; declarative bindings - a simple and obvious way to connect parts of the UI to the data model; flexible and sophisticated templating - construct a complex dynamic UI easily using arbitrarily nested templates; trivially extensible - implement custom behaviors as new declarative bindings for easy reuse in just a few lines of code.

Additional benefits of using the library are:

  • Pure JavaScript library - works with any server or client-side technology
  • Can be added on top of your existing web application without requiring major architectural changes
  • Compact - around 25kb before gzipping
  • Works on any mainstream browser (IE 6+, Firefox 2+, Chrome, Safari, others)
  • Comprehensive suite of specifications (developed BDD-style) means its correct functioning can easily be verified on new browsers and platforms

Knockout is not a replacement of any JavaScript library. On the contrary it lets you scale up in complexity without fear of introducing inconsistencies.