Knockout.js

ko.observable creates a value that Knockout can track for changes. When the observable changes, dependent parts of the page can update automatically without manually editing the DOM.

Knockout uses declarative data-bind attributes in HTML to connect controls to a view model. Calling ko.applyBindings starts that connection, allowing values such as text, visibility, and form fields to follow JavaScript state.

A computed observable derives its value from other observables and tracks those dependencies automatically. For example, a total price can recalculate when a quantity or unit-price observable changes.

Knockout is especially useful when maintaining an existing interface built around its MVVM pattern and data-bind syntax. React and Vue are more common choices for many new applications, but Knockout can still be practical when a project already depends on observable view models.