In a Virtual DOM, diffing is the process of comparing the current state of the virtual representation with a new state and determining the minimal set of modifications needed to update the real DOM. The diffing algorithm in Virtual DOM is designed to be efficient and minimize the number of changes required.

  Here is a high-level overview of how diffing works in a Virtual DOM:

  1. Create a virtual representation: The current state of the application is represented as a virtual tree structure of components and elements. This virtual tree is a lightweight in-memory representation of the real DOM.

  2. Update the virtual tree: When changes occur in the application, the virtual tree is updated to reflect the new state. This can involve adding, removing, or updating components and elements in the tree.

  3. Perform a diff: The current virtual tree is compared with the previous virtual tree to identify the differences between the two.

  4. Generate a patch: The differences between the current and previous virtual trees are analyzed to create a patch, which is a minimal set of instructions required to update the real DOM.

  5. Apply the patch: The patch is applied to the real DOM to update it accordingly. This involves adding, removing, or updating the actual DOM elements as needed.

  The diffing algorithm in the Virtual DOM is designed to be efficient by minimizing unnecessary operations. It uses various techniques, such as tree differencing and smart updating, to optimize the process. For example, instead of traversing the entire tree, the diffing algorithm may focus only on specific branches or components that have changed.

  Overall, the diffing process in Virtual DOM helps improve performance by reducing the number of DOM operations needed to update the UI. It allows for efficient rendering and keeps the application responsive even when there are frequent updates to the state.