What is the reactivity system in Frontend

June 28, 2023

   The reactivity system is a fundamental feature that enables automatic and efficient updating of the user interface when the underlying data changes. It is one of the key aspects that make a reactive framework.

   The reactivity system in Vue.js revolves around the concept of "reactive" objects, which are essentially JavaScript objects that Vue is able to track and observe for changes. When a reactive object's property is modified, Vue.js automatically detects the change and updates the corresponding part of the user interface to reflect the new value.

The reactivity system operates based in some principles:

  When a component renders, Vue.js records all the dependencies (such as reactive properties and computed properties) accessed during the rendering process. This establishes a dependency relationship between the component and the data it relies on. 

    Vue.js utilizes a technique called "dirty checking" to detect changes in reactive objects. It periodically re-evaluates the reactive getters to see if any dependencies have changed. If a change is detected, Vue.js triggers the necessary updates to the affected parts of the user interface.

    Vue.js replaces the original properties of a reactive object with special getters and setters. These getters and setters are responsible for tracking dependencies and triggering updates when necessary. Whenever a reactive property is accessed or modified, the corresponding getter or setter is invoked, allowing Vue.js to keep track of dependencies. 

    To optimize performance, Vue.js batches multiple updates together. Instead of immediately updating the user interface for every single change, it queues the updates and performs them in batches during the next tick of the event loop. This way, unnecessary duplicate updates are avoided, resulting in improved efficiency.

    The reactivity system in Vue.js plays a crucial role in creating responsive and interactive user interfaces. By automatically tracking dependencies and efficiently updating the UI, developers can focus on writing the application logic without having to worry about manually synchronizing the data and the view.

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