How React Works (Part 2)? Why React Had to Build Its Own Execution Engine

The article provides a detailed explanation of how React's internal architecture, specifically its Scheduler and Reconciler components, enables efficient and responsive user interfaces. Here are the key points:

1. Problem with JavaScript Call Stack: Traditional rendering in React was done using a continuous chain of function calls (JavaScript call stack). This approach is simple but doesn't allow for interruptible or prioritized rendering, which modern applications require.

2. Introduction of Fiber Architecture:

   • Fiber Nodes: React introduced a tree structure made up of plain JavaScript objects called "fibers." Each fiber acts like a stack frame that the React engine can control.
   • Two Trees: React maintains two versions of the component tree at all times: the current tree (what's currently displayed) and the work-in-progress tree (being built for the next render). This ensures that rendering doesn't disrupt what is shown on screen.

3. Scheduler:

   • The Scheduler module decides when and in what order to run tasks.
   • It can pause, resume, prioritize, or abort rendering based on the current context and incoming updates.
   • Prioritization: React can switch to handling higher-priority tasks (like user input) before completing lower-p

Read the full article at DEV Community

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