React has its own mechanism of how it determines which component should be updated first. It does not update everything at the same time. It checks the changes, gives priority, and updates them step by step. This is the deeper understanding of how React works. This is usually explained in a React JS Online Course while learning how React handles performance.

How the Update Process Starts?

When there is a change in the props or the state of a component, React starts the update process. It creates a new update record. This record is kept inside the node of the component. Every component has its own place where the update record is kept. It is given a priority level.

Fiber Tree and Component

React has a system called a Fiber Tree, which means that every component in the React application is connected in a tree-like manner. The React library always checks from the top and moves down.

It does not check randomly, and it moves in a predetermined manner:

• Parent component


• Child component


• Sibling component

This ensures that the React library maintains a clean and consistent update process.

Priority System (Lanes)

React has a system of lanes, which means that not all updates in the React application are equal.

Simple view:

• High priority: user actions (click, typing)


• Medium priority: UI changes


• Low priority: background updates

This explains why typing in a React application is fast, whereas other updates take a long time. This is a critical part of the React Certification, as it has a direct impact on the speed of the React application.

Reconciliation Process

React always compares old and new data, and if it has changed, it updates it accordingly, whereas if it has not changed, it skips it.

Checks:

• Has the state changed?


• Have the props changed?


• Is the component the same or different?

Update Phases

React updates happen in two main steps.

Important point:

• Render phase can pause


• Commit phase runs fast and completes the update

Batching of Updates

React processes multiple updates together, which is called "batching."

Why it matters:

• Reduces number of re-renders


• Increases speed


• Maintains smoothness

Points to remember:

• Multiple updates = one render cycle


• Happens automatically in modern React

This phenomenon is easier to grasp while developing an app through a React JS Course in Delhi, where multiple updates take place simultaneously.

Depth-First Update Order

React follows a depth-first order to check components.

Simple flow:

• Start from the root


• Go deep into the child


• Then go to the sibling

This way, the components update together.

Role of Keys

• Keys help React identify items in a list.


• Without keys, React has to check the entire list.


• With keys, React only updates the items that have changed.

Points:

• Keys should be unique


• Helps in faster updates


• Unnecessary rendering avoided

Skipping Unnecessary Updates

React skips updating if nothing has changed.

Tools used:

• Memo


• Pure comparison

Benefits:

• Less processing


• Faster UI


• Better performance

Concurrent Rendering

React can pause work and handle more important updates first.

What it means:

• Can stop one update


• Can start another


• Can resume later

This keeps the app responsive even under load.

Update Queue System

Each component has its own update queue.

Key Points:

• Updates are stored locally.


• React only checks the parts that need to be updated.


• The entire tree does not need to be checked every time.

This is one of the reasons why React is good for large applications.

Real Learning Insight

While learning from a React JS Online Course, most people get caught up in the actual code-writing part. However, this insight into the update process makes a world of difference in actual projects.

In actual projects, if updates are not handled well, the screen becomes slow, and the rendering gets stuck, which is a problem faced during a React JS Course in Delhi.

Sum up,

React follows a smart update process. It knows exactly what to update, in which order, and so on. It never wastes its resources. This is exactly why React is good for large applications. Learning this process helps to create better code.